The effects of Yb/Zr micro-alloying on the microstructure,mechanical properties,and corrosion resistance of an Al-Zn-Mg-Cu alloy were systematically investigated.Upon the addition of Yb/Zr to the Al-Zn-Mg-Cu alloy,the...The effects of Yb/Zr micro-alloying on the microstructure,mechanical properties,and corrosion resistance of an Al-Zn-Mg-Cu alloy were systematically investigated.Upon the addition of Yb/Zr to the Al-Zn-Mg-Cu alloy,the grain boundaries were pinned by high-density nanosized Al_(3)(Yb,Zr)precipitates during extrusion deformation,consequently,the average grain size was significantly reduced from 232.7μm to 3.2μm.This grain refinement contributed substantially to the improvement in both strength and elongation.The ultimate tensile strength,yield strength,and elongation of the Yb/Zr modified alloy increased to 705.3 MPa,677.6 MPa,and 8.7%,respectively,representing enhancements of 16.2%,19.3%,and 112.2%compared to the unmodified alloy.Moreover,the distribution of MgZn_(2)phases along grain boundaries became more discontinuous in the Yb/Zr modified alloy,which effectively retarded the propagation of intergranular corrosion and improved the corrosion resistance.展开更多
The effects of different warm rolling(WR)reductions on the microstructure and mechanical properties of low-Cr FeCrAl alloys at both room and elevated temperatures were investigated.The study revealed that when the WR ...The effects of different warm rolling(WR)reductions on the microstructure and mechanical properties of low-Cr FeCrAl alloys at both room and elevated temperatures were investigated.The study revealed that when the WR reduction is small,it effectively refines the grains and forms a large number of subgrains in the matrix,while also inducing the dissolution of the Laves phase.This enhances the mechanical properties of FeCrAl alloys primarily through grain refinement and solid solution strengthening.Conversely,with larger WR reductions,the grain refinement effect diminishes,but a significant number of Laves phases form in the matrix,strengthening the alloys primarily through precipitation strengthening.WR exhibited a remarkable enhancing effect on the comprehensive mechanical properties at both room and high temperatures,with a signi-ficant enhancement in ductility at high temperatures.Notably,a 10%WR reduction resulted in the optimal overall mechanical properties at both room and elevated temperatures.展开更多
High-entropy alloys(HEAs)with multi-component elements have attracted significant interest since they exhibit numerous superior properties compared to traditional ones.These properties include significant energy relea...High-entropy alloys(HEAs)with multi-component elements have attracted significant interest since they exhibit numerous superior properties compared to traditional ones.These properties include significant energy release,remarkable fracture toughness,and high strength,making them promising candidates as energetic structural materials(ESMs).This paper summarizes the energy release mechanisms under dynamic impact and the mechanical behavior of TiZr-based HEAs,TiNb-based HEAs,andWbased HEA,including velocity threshold for energy release,chamber quasi-static pressure curve,energy release efficiency,interface reactions,and"self-sharpening".In addition,we propose future research directions for their energy release and mechanical behavior.展开更多
This work aimed to(i)understand conventional and pulse gas tungsten arc welding(GTAW)of AZ31B,and(ii)explore high frequency welding(100 Hz-1500 Hz).GTA welding with alternating current(AC)and direct current electrode ...This work aimed to(i)understand conventional and pulse gas tungsten arc welding(GTAW)of AZ31B,and(ii)explore high frequency welding(100 Hz-1500 Hz).GTA welding with alternating current(AC)and direct current electrode positive(DCEP)polarities yielded crack-free partial penetration welds for6 mm thick AZ31B alloy sheet.Welding under direct current electrode negative(DCEN)polarity with identical parameters as that for AC and DCEP resulted in full penetration welds that had microcracks.Defect-free full-penetration welds could be accomplished with pulse GTA welding using DCEN polarity at a pulse frequency of 1 Hz with a pulse duration ratio of 1:1.The resultant DCEN P 1:1 weld metal had a microstructure finer than the conventional DCEN weld.Welds produced with pulse duration ratios of 1:2and 1:4 lacked penetration but had a much finer microstructures because of the lower heat input.The arc constriction by the high frequency pulsing in the Activ Arc■-High frequency(AA-HF)mode welding was responsible for deeper penetration.Welds produced under DCEN pulsing and AA-HF conditions had hardness higher than conventional DCEN,DCEP and AC GTA welds,attributed to the finer microstructure.AA-HF GTA welding produced defect free deeper penetration welds with good microstructural features/mechanical properties and also gave an advantage of 50%enhanced productivity when welded at1500 Hz.展开更多
In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 ...In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 aluminum alloy are studied.The result show that ECAP induces numerous substructures and dislocations,effectively promoting the precipitation of theηʹphase exhibiting a bimodal structure during inter-pass aging.Following inter-pass aging and subsequent ECAP,the decrease in grain size(4.8μm)is together with the increase in dislocation density(1.24×10^(15) m^(−2))due to the pinning effect of the precipitated phase.Simultaneously,the dislocation motion causes the second phase particles to become even finer and more diffuse.The synergistic effects of precipitation strengthening,fine grain strengthening,and dislocation strengthening collectively enhance the high strength of aluminum alloys,with ultimate tensile strength and yield strength reaching approximately 610 and 565 MPa,respectively.Meanwhile,ductility remains largely unchanged,primarily due to coordinated grain boundary sliding and the uniform and fine dispersion of second phase particles.展开更多
In the present study,the mechanical and ballistic properties of friction stir welded(FSW)aluminum alloy(AA5754)samples were investigated,both untreated and cryogenically treated,when impacted by a 7.62 mm armour-pierc...In the present study,the mechanical and ballistic properties of friction stir welded(FSW)aluminum alloy(AA5754)samples were investigated,both untreated and cryogenically treated,when impacted by a 7.62 mm armour-piercing(AP)bullet at an impact velocity of 682±20 m/s.The FSW technique was used to prepare the welded samples for AA5754,with an axial force of 7 kN,a feed rate of 20 mm/min,and a speed of 1200 rpm.The cryogenic treatments performed after welding,including deep cryogenic treatment(DCT)at196℃ and shallow cryogenic treatment(SCT)at80℃,for 6 and 72 h,respectively.The microstructure and mechanical characteristics of cryogenically treated and untreated joints were examined.The cryogenic treatment refined the grain size(1.05 μm)and enhanced the microhardness(93 Hv).Moreover,DCT-FSW significantly improved the tensile strength(13.93%)and impact strength(8.45%)compared to untreated FSW sample.Additionally,in untreated FSW samples,the fracture behaviour varied:the impact fracture mode primarily exhibited ductile failure,while the tensile fracture exhibited a mixed fracture mode.In contrast,the tensile and impact fracture modes of the DCT-FSWwere dominated by a ductile failure mode.The DCT-FSW target demonstrated a lower depth of penetration(DOP)of 31 mm compared to the SCT-FSWand untreated FSW targets.Post-ballistic SEM analysis in the crater region of all three zones revealed the formation of frictional grooves,small cracks,and adiabatic shear bands(ASBs).展开更多
High-entropy alloy composites(HEACs)have attracted significant attention due to their exceptional mechanical properties and chemical stability.By adjusting the content of reinforcing particles in the high-entropy allo...High-entropy alloy composites(HEACs)have attracted significant attention due to their exceptional mechanical properties and chemical stability.By adjusting the content of reinforcing particles in the high-entropy alloy and by employing advanced additive manufacturing techniques,high-performance HEACs can be fabricated.However,there is still considerable room for improvement in their performance.In this study,CoCrFeMnNi HEA powders were used as the matrix,and NiCoFeAlTi high-entropy intermetallic powders were used as the high-entropy reinforcement(HER).CoCrFeMnNi/NiCoFeAlTi HEACs were fabricated using selective laser melting technology.The study results indicate that after aging,the microstructure of HEACs with HER exhibits Al-and Ti-rich nano-oxide precipitates with an orthorhombic CMCM type structure system.After aging at 873 K for 2 h,HEACs with HER achieved excellent overall mechanical properties,with an ultimate tensile strength of 731 MPa.This is attributed to the combined and synergistic effects of precipitation strengthening,dislocation strengthening,and the high lattice distortion caused by high intragranular defects,which provide a multi-scale strengthening and hardening mechanism for the plastic deformation of HEACs with HER.This study demonstrates that aging plays a crucial role in controlling the precipitate phases in complex multi-element alloys.展开更多
The high entropy alloys(HEAs)are the newly developed high-performance materials that have gained significant importance in defence,nuclear and aerospace sector due to their superior mechanical properties,heat resistan...The high entropy alloys(HEAs)are the newly developed high-performance materials that have gained significant importance in defence,nuclear and aerospace sector due to their superior mechanical properties,heat resistance,high temperature strength and corrosion resistance.These alloys are manufactured by the equal mixing or larger proportions of five or more alloying elements.HEAs exhibit superior mechanical performance compared to traditional engineering alloys because of the extensive alloying composition and higher entropy of mixing.Solid state welding(SSW)techniques such as friction stir welding(FSW),rotary friction welding(RFW),diffusion bonding(DB)and explosive welding(EW)have been efficiently deployed for improving the microstructural integrity and mechanical properties of welded HEA joints.The HEA interlayers revealed greater potential in supressing the formation of deleterious intermetallic phases and maximizing the mechanical properties of HEAs joints.The similar and dissimilar joining of HEAs has been manifested to be viable for HEA systems which further expands their industrial applications.Thus,the main objective of this review paper is to present a critical review of current state of research,challenges and opportunities and main directions in SSW of HEAs mainly CoCrFeNiMn and Al_xCoCrFeNi alloys.The state of the art of problems,progress and future outlook in SSW of HEAs are critically reviewed by considering the formation of phases,microstructural evolution and mechanical properties of HEAs joints.展开更多
The effect of Ti addition on microstructure and mechanical properties of Zn-22Al eutectoid alloy with 0.15 wt%Ti was investigated.It was observed that the presence of Ti changes the morphology of n phase in the alloy....The effect of Ti addition on microstructure and mechanical properties of Zn-22Al eutectoid alloy with 0.15 wt%Ti was investigated.It was observed that the presence of Ti changes the morphology of n phase in the alloy.Addition of Ti to Zn-Al alloy caused the formation of Ti(Zn,Al)_(3);phase.Before applying equal channel angular pressing(ECAP),two times of homogenization treatment were conducted on the alloy.After secondary homogenization,the microstructure consisted of a homogeneous and fine mixture ofαand n phases and the as-cast lamellar structure removed.After homogenization,ECAP was carried out on Ti-containing Zn-22Al alloy.The fraction of high angle grain boundaries increased with increasing the number of ECAP passes.The average grain size reduced from 930 nm after secondary homogenization to 380 nm after 8 passes of ECAP.The texture of the alloy also changed by applying ECAP.Maximum elongation to failure of the homogenized alloy was 135%at a strain rate of 10^(-5)s^(-1)which enhanced to a maximum of 405%at a strain rate of 10^(-3)s^(-1)after 8 passes of ECAP.It was also observed that by conducting ECAP and increasing the number of passes the hardness decreases,which indicates work-softening behavior due to dynamic recovery/recrystallization.展开更多
In this work,a novel type of short-process deformation technology of Mg alloys,bifurcation-equal channel angular pressing(B-ECAP),was proposed to refine grain and improve the basal texture.The cylindrical billets were...In this work,a novel type of short-process deformation technology of Mg alloys,bifurcation-equal channel angular pressing(B-ECAP),was proposed to refine grain and improve the basal texture.The cylindrical billets were first compressed into the die cavity,then sequentially flowed downward through a 90°corner and two 120°shear steps.The total strain of B-ECAP process could reach 3.924 in a single pass.The results of microstructure observation showed that DRX occurred at upsetting process in the die cavity and completed at position D.The grains were refined to 6.3μm at being extruded at 300℃ and grew obviously with the extrusion temperature increase.The shear tress induced by 900 corner and two 120°shear steps resulted in the basal poles of most grains tilted to extrusion direction(ED)by±25°.Compared with the original billets,the extruded sheets exhibited higher yield strengths(YS),which was mainly attributed to the grain refinement.The higher Schmid factor caused by ED-tilt texture resulted in a fracture elongation(FE)more than that of the original bar in ED,while was equivalent to that in transverse direction(TD).As the extrusion temperature increased,the variation of UTS and YS in ED and TD decreased gradually without ductility obviously decrease.展开更多
The evolution of mechanical properties,localized corrosion resistance of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging(NIA)was investigated by hardness test,electrical conductivity test,tensile test,inte...The evolution of mechanical properties,localized corrosion resistance of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging(NIA)was investigated by hardness test,electrical conductivity test,tensile test,intergranular corrosion test,exfoliation corrosion test,slow strain rate tensile test and electrochemical test,and the mechanism has been discussed based on microstructure examination by optical microscopy,electron back scattered diffraction,scanning electron microscopy and scanning transmission electron microscopy.The NIA treatment includes a heating stage from 40℃to 180℃with a rate of 20℃/h and a cooling stage from 180℃to 40℃with a rate of 10℃/h.The results show that the hardness and strength increase rapidly during the heating stage of NIA since the increasing temperature favors the nucleation and the growth of strengthening precipitates and promotes the transformation of Guinier-Preston(GPI)zones toη'phase.During the cooling stage,the sizes ofη'phase increase with a little change in the number density,leading to a further slight increase of the hardness and strength.As NIA proceeds,the corroded morphology in the alloy changes from a layering feature to a wavy feature,the maximum corrosion depth decreases,and the reason has been analyzed based on the microstructural and microchemical feature of precipitates at grain boundaries and subgrain boundaries.展开更多
The slow degration of iron limits its bone implant application.The solid solution of Zn in Fe is expected to accelerate the degradation.In this work,mechanical alloying(MA)was used to prepare Fe-Zn powder with supersa...The slow degration of iron limits its bone implant application.The solid solution of Zn in Fe is expected to accelerate the degradation.In this work,mechanical alloying(MA)was used to prepare Fe-Zn powder with supersaturated solid solution.MA significantly decreased the lamellar spacing between particles,thus reducing the diffusion distance of solution atoms.Moreover,it caused a number of crystalline defects,which further promoted the solution diffusion.Subsequently,the MA-processed powder was consolidated into Fe-Zn part by laser sintering,which involved a partial melting/rapid solidification mechanism and retained the original supersaturated solid solution.Results proved that the Fe-Zn alloy became more susceptible with a lowered corrosion potential,and thereby an accelerated corrosion rate of(0.112±0.013)mm/year.Furthermore,it also exhibited favorable cell behavior.This work highlighted the advantage of MA combined with laser sintering for the preparation of Fe-Zn implant with improved degradation performance.展开更多
In this study,the Mg-3Zn-0.5Zr-χNd(χ=0,0.6)alloys were subjected to final rolling treatment with large deformation of 50%.The impact of annealing temperatures on the microstructure and mechanical properties was inve...In this study,the Mg-3Zn-0.5Zr-χNd(χ=0,0.6)alloys were subjected to final rolling treatment with large deformation of 50%.The impact of annealing temperatures on the microstructure and mechanical properties was investigated.The rolled Mg-3Zn-0.5Zr-0.6Nd alloy exhibited an ultimate tensile strength of 386 MPa,a yield strength of 361 MPa,and an elongation of 7.1%.Annealing at different temperatures resulted in reduced strength and obviously increased elongation for both alloys.Optimal mechanical properties for the Mg-3Zn-0.5Zr-0.6Nd alloy were achieved after annealing at 200℃,with an ultimate tensile strength of 287 MPa,a yield strength of 235 MPa,and an elongation of 26.1%.The numerous deformed microstructures,twins,and precipitated phases in the rolled alloy could impede the deformation at room temperature and increase the work hardening rate.After annealing,a decrease in the work hardening effect and an increase in the dynamic recovery effect were obtained due to the formation of fine equiaxed grains,and the increased volume fraction of precipitated phases,which significantly improved the elongation of the alloy.Additionally,the addition of Nd element could enhance the annealing recrystallization rate,reduce the Schmid factor difference between basal and prismatic slip systems,facilitate multi-system slip initiation and improve the alloy plasticity.展开更多
In this study,specific warm rolling was carried out to process the Fe_(50)Mn_(30)Co_(10)Cr_(10) high-entropy alloy.The aim was to investigate the effect of warm rolling temperature on the microstructure and mechanical...In this study,specific warm rolling was carried out to process the Fe_(50)Mn_(30)Co_(10)Cr_(10) high-entropy alloy.The aim was to investigate the effect of warm rolling temperature on the microstructure and mechanical properties.The results indicated that serious transverse cracks appeared in the 25℃ rolled sheet with reduction of 60%,which was significantly improved through 100−300℃ warm rolling.In addition,the increase of rolling temperature promoted dislocation slip and inhibited martensitic transformation and twinning deformation.A single face centered cubic(FCC)matrix with abundant dislocations and stacking faults was developed in the 300℃rolled microstructure.Meanwhile,the deformation stored energy gradually increased,and the copper-type deformation texture was gradually enhanced.After annealing,the recrystallized microstructure of 25−200℃ rolled sheets was composed of FCC and a small amount of HCP phase.However,the hexagonal close packed(HCP)content in the annealed sheet rolled at 300℃ was as high as 20%−23% after annealing for 2−4 min and decreased to 4.5%after annealing for 8 min.All recrystallized microstructure contained a large number of annealing twins,and the average grain size increased with the increase of rolling temperature.Moreover,the mechanical properties of the annealed sheet were significantly improved after warm rolling.展开更多
Structural evolution of alloys by ball milling during solid state amorphization were studied by means of XAFS technique. The first one is amorphization process of Fe and B powder mixtures by mechanical alloying (MA), ...Structural evolution of alloys by ball milling during solid state amorphization were studied by means of XAFS technique. The first one is amorphization process of Fe and B powder mixtures by mechanical alloying (MA), and the second one is amorphization process of ordered B2 CoZr intermetallic compound by mechanical milling (MM). The mixing process of Fe and B and disintegration process of ordered B2 CoZr intermetallic compound crystal were observed clearly in atomic level by XAFS method. The micro mechanism of amorphization process of alloy by ball milling was discussed.展开更多
Zr50Al15Ni10Cu25 amorphous powder was synthesized by mechanical alloying. The effect of Si3N4 addition on the crystallization behavior of the alloy during sintering process was studied. Thermal stability of the powder...Zr50Al15Ni10Cu25 amorphous powder was synthesized by mechanical alloying. The effect of Si3N4 addition on the crystallization behavior of the alloy during sintering process was studied. Thermal stability of the powders was performed by differential scanning calorimetry （DSC）. The phase and microstructure of the powders and bulk specimens sintered were determined by X-ray diffractometry （XRD） and scanning electron microscopy （SEM）. The results show that, introducing 0.05% （mass fraction） Si3N4 can enhance the crystallization activation energy of the ZZr50Al15Ni10Cu25 amorphous powders, which indicates that Si3N4 addition has hindrance effect on forming crystals from Zr50Al15Ni10Cu25amorphous powder. However, 0.10% Si3N4 results in the decrease of the crystallization activation energy, which makes its crystallization process easy to occur.展开更多
The mechanical properties and deformation features of AZ31-0.84% Sb alloy have been studied by means of the measurement of the properties and morphology observation. Results show that UTS of AZ31-0.84% Sb alloy at roo...The mechanical properties and deformation features of AZ31-0.84% Sb alloy have been studied by means of the measurement of the properties and morphology observation. Results show that UTS of AZ31-0.84% Sb alloy at room temperature is 297MPa, a higher value of UTS is still maintained up to 189MPa as temperature elevated to 200℃. One of the main reasons for enhancing UTS of the alloy is attributed to the high volume fraction of the precipitates dispersed in the matrix, including Mg3Sb2 phase, which effectively hindered the movement of dislocations during the elevated temperature deformation. The deformation mechanisms of AZ31-0.84% Sb alloy are the twins and dislocations activated on basal and non-basal planes. a+c dislocations may be activated on the basal and non-basal planes in twins regions, and some of the thinner twins may shear through the dense dislocations within the thicker twins.展开更多
The microstructural evolution and mechanical properties of high speed indirect-extruded Mg-5%Sn-(1, 2, 4) Zn(mass fraction, %) alloys were investigated by optical microscopy(OM), X-ray diffraction(XRD), scanning elect...The microstructural evolution and mechanical properties of high speed indirect-extruded Mg-5%Sn-(1, 2, 4) Zn(mass fraction, %) alloys were investigated by optical microscopy(OM), X-ray diffraction(XRD), scanning electron microscopy(SEM), differential thermal analysis(DTA) and a static tension tester. All the studied alloys can be extruded successfully at a high speed of 10 m/min. The grain size, area fraction of particles and tensile properties are found to be greatly affected by the extrusion speed and Zn content, resulting in tensile properties showing lower strength and ductility as the extrusion speed increases and Zn content decreases. The dependence of grain size and tensile properties on the second phase particles is also discussed.展开更多
Mechanical properties and tribological behavior of a novel cast heat resisting copper based alloy are investigated. The corresponding properties of a commercial aluminum bronze C95500 (ASTM B30) are compared with the ...Mechanical properties and tribological behavior of a novel cast heat resisting copper based alloy are investigated. The corresponding properties of a commercial aluminum bronze C95500 (ASTM B30) are compared with the alloy. The results show that the alloy possesses better mechanical properties and tribological behaviors than that of C95500 at elevated temperature. The tensile strength, elongation and hardness at 500℃ are 470MPa, 2.5% and HB220, respectively. The wear rate of the developed alloy at ambient and elevated temperature is about one sixth and one fortieth of that of C95500, respectively. The alloy is very suitable for ma nufacturing heat resisting and wear resisting parts. Major strengthening mechanisms for the alloy are solution strengthening and the second phase strengthening.展开更多
The mechanical properties and microstructure of Al-Cu-Li alloy sheets subjected to cryorolling(-100 ° C,-190 ℃) or hot rolling(400 ℃) and subsequent aging at 160 ℃ for different times were investigated. The dy...The mechanical properties and microstructure of Al-Cu-Li alloy sheets subjected to cryorolling(-100 ° C,-190 ℃) or hot rolling(400 ℃) and subsequent aging at 160 ℃ for different times were investigated. The dynamic precipitation and dislocation characterizations were examined via transmission electron microscopy and X-ray diffraction. The grain morphologies and the fracture-surface morphologies were studied via optical microscopy and scanning electron microscopy. Samples subjected to cryorolling followed by aging exhibited relatively high dislocation densities and a large number of precipitates compared with hot-rolled samples. The samples cryorolled at-190 ℃ and then aged for 15 h presented the highest ultimate tensile strength(586 MPa), while the alloy processed via hot rolling followed by 10 h aging exhibited the highest uniform elongation rate(11.5%). The size of precipitates increased with the aging time, which has significant effects on the interaction mechanism between dislocations and precipitates. Bowing is the main interaction method between the deformation-induced dislocations and coarsened precipitates during tensile tests, leading to the decline of the mechanical properties of the alloy during overaging. These interesting findings can provide significant insights into the development of materials possessing both excellent strength and high ductility.展开更多
基金Project(51501228)supported by the National Natural Science Foundation of ChinaProject(202109)supported by the Open Sharing Fund for the Large-scale Instruments and Equipments of Central South University,China。
文摘The effects of Yb/Zr micro-alloying on the microstructure,mechanical properties,and corrosion resistance of an Al-Zn-Mg-Cu alloy were systematically investigated.Upon the addition of Yb/Zr to the Al-Zn-Mg-Cu alloy,the grain boundaries were pinned by high-density nanosized Al_(3)(Yb,Zr)precipitates during extrusion deformation,consequently,the average grain size was significantly reduced from 232.7μm to 3.2μm.This grain refinement contributed substantially to the improvement in both strength and elongation.The ultimate tensile strength,yield strength,and elongation of the Yb/Zr modified alloy increased to 705.3 MPa,677.6 MPa,and 8.7%,respectively,representing enhancements of 16.2%,19.3%,and 112.2%compared to the unmodified alloy.Moreover,the distribution of MgZn_(2)phases along grain boundaries became more discontinuous in the Yb/Zr modified alloy,which effectively retarded the propagation of intergranular corrosion and improved the corrosion resistance.
文摘The effects of different warm rolling(WR)reductions on the microstructure and mechanical properties of low-Cr FeCrAl alloys at both room and elevated temperatures were investigated.The study revealed that when the WR reduction is small,it effectively refines the grains and forms a large number of subgrains in the matrix,while also inducing the dissolution of the Laves phase.This enhances the mechanical properties of FeCrAl alloys primarily through grain refinement and solid solution strengthening.Conversely,with larger WR reductions,the grain refinement effect diminishes,but a significant number of Laves phases form in the matrix,strengthening the alloys primarily through precipitation strengthening.WR exhibited a remarkable enhancing effect on the comprehensive mechanical properties at both room and high temperatures,with a signi-ficant enhancement in ductility at high temperatures.Notably,a 10%WR reduction resulted in the optimal overall mechanical properties at both room and elevated temperatures.
基金the funding from the Overseas Young Talents Program(22GAA00842)the Hebei Natural Science Foundation(E2024105032)+4 种基金the Youth Academic Startup Program at Beijing Institute of Technology(RCPT-6120210286)the"National Key Laboratory Foundation of Science and Technology on Materials under Shock and Impact(No.WDZC2022-1)""National Natural Science Foundation of China(No.52271141)"the support of"National Natural Science Foundation of China(Grant No.12222204 and 12072045)"the support of"National Natural Science Foundation of China(Grant No.52331006)".
文摘High-entropy alloys(HEAs)with multi-component elements have attracted significant interest since they exhibit numerous superior properties compared to traditional ones.These properties include significant energy release,remarkable fracture toughness,and high strength,making them promising candidates as energetic structural materials(ESMs).This paper summarizes the energy release mechanisms under dynamic impact and the mechanical behavior of TiZr-based HEAs,TiNb-based HEAs,andWbased HEA,including velocity threshold for energy release,chamber quasi-static pressure curve,energy release efficiency,interface reactions,and"self-sharpening".In addition,we propose future research directions for their energy release and mechanical behavior.
文摘This work aimed to(i)understand conventional and pulse gas tungsten arc welding(GTAW)of AZ31B,and(ii)explore high frequency welding(100 Hz-1500 Hz).GTA welding with alternating current(AC)and direct current electrode positive(DCEP)polarities yielded crack-free partial penetration welds for6 mm thick AZ31B alloy sheet.Welding under direct current electrode negative(DCEN)polarity with identical parameters as that for AC and DCEP resulted in full penetration welds that had microcracks.Defect-free full-penetration welds could be accomplished with pulse GTA welding using DCEN polarity at a pulse frequency of 1 Hz with a pulse duration ratio of 1:1.The resultant DCEN P 1:1 weld metal had a microstructure finer than the conventional DCEN weld.Welds produced with pulse duration ratios of 1:2and 1:4 lacked penetration but had a much finer microstructures because of the lower heat input.The arc constriction by the high frequency pulsing in the Activ Arc■-High frequency(AA-HF)mode welding was responsible for deeper penetration.Welds produced under DCEN pulsing and AA-HF conditions had hardness higher than conventional DCEN,DCEP and AC GTA welds,attributed to the finer microstructure.AA-HF GTA welding produced defect free deeper penetration welds with good microstructural features/mechanical properties and also gave an advantage of 50%enhanced productivity when welded at1500 Hz.
基金Project(52275350)supported by the National Natural Science Foundation of ChinaProject(0301006)supported by the International Cooperative Scientific Research Platform of SUES,China。
文摘In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 aluminum alloy are studied.The result show that ECAP induces numerous substructures and dislocations,effectively promoting the precipitation of theηʹphase exhibiting a bimodal structure during inter-pass aging.Following inter-pass aging and subsequent ECAP,the decrease in grain size(4.8μm)is together with the increase in dislocation density(1.24×10^(15) m^(−2))due to the pinning effect of the precipitated phase.Simultaneously,the dislocation motion causes the second phase particles to become even finer and more diffuse.The synergistic effects of precipitation strengthening,fine grain strengthening,and dislocation strengthening collectively enhance the high strength of aluminum alloys,with ultimate tensile strength and yield strength reaching approximately 610 and 565 MPa,respectively.Meanwhile,ductility remains largely unchanged,primarily due to coordinated grain boundary sliding and the uniform and fine dispersion of second phase particles.
文摘In the present study,the mechanical and ballistic properties of friction stir welded(FSW)aluminum alloy(AA5754)samples were investigated,both untreated and cryogenically treated,when impacted by a 7.62 mm armour-piercing(AP)bullet at an impact velocity of 682±20 m/s.The FSW technique was used to prepare the welded samples for AA5754,with an axial force of 7 kN,a feed rate of 20 mm/min,and a speed of 1200 rpm.The cryogenic treatments performed after welding,including deep cryogenic treatment(DCT)at196℃ and shallow cryogenic treatment(SCT)at80℃,for 6 and 72 h,respectively.The microstructure and mechanical characteristics of cryogenically treated and untreated joints were examined.The cryogenic treatment refined the grain size(1.05 μm)and enhanced the microhardness(93 Hv).Moreover,DCT-FSW significantly improved the tensile strength(13.93%)and impact strength(8.45%)compared to untreated FSW sample.Additionally,in untreated FSW samples,the fracture behaviour varied:the impact fracture mode primarily exhibited ductile failure,while the tensile fracture exhibited a mixed fracture mode.In contrast,the tensile and impact fracture modes of the DCT-FSWwere dominated by a ductile failure mode.The DCT-FSW target demonstrated a lower depth of penetration(DOP)of 31 mm compared to the SCT-FSWand untreated FSW targets.Post-ballistic SEM analysis in the crater region of all three zones revealed the formation of frictional grooves,small cracks,and adiabatic shear bands(ASBs).
基金Project supported by ClassⅢPeak Discipline of Shanghai-Materials Science and Engineering(High-Energy Beam Intelligent Processing and Green Manufacturing),China。
文摘High-entropy alloy composites(HEACs)have attracted significant attention due to their exceptional mechanical properties and chemical stability.By adjusting the content of reinforcing particles in the high-entropy alloy and by employing advanced additive manufacturing techniques,high-performance HEACs can be fabricated.However,there is still considerable room for improvement in their performance.In this study,CoCrFeMnNi HEA powders were used as the matrix,and NiCoFeAlTi high-entropy intermetallic powders were used as the high-entropy reinforcement(HER).CoCrFeMnNi/NiCoFeAlTi HEACs were fabricated using selective laser melting technology.The study results indicate that after aging,the microstructure of HEACs with HER exhibits Al-and Ti-rich nano-oxide precipitates with an orthorhombic CMCM type structure system.After aging at 873 K for 2 h,HEACs with HER achieved excellent overall mechanical properties,with an ultimate tensile strength of 731 MPa.This is attributed to the combined and synergistic effects of precipitation strengthening,dislocation strengthening,and the high lattice distortion caused by high intragranular defects,which provide a multi-scale strengthening and hardening mechanism for the plastic deformation of HEACs with HER.This study demonstrates that aging plays a crucial role in controlling the precipitate phases in complex multi-element alloys.
基金financially supported by Ministry of Science and Higher Education of the Russian Federation(Grant No.FENU-2023-0013)。
文摘The high entropy alloys(HEAs)are the newly developed high-performance materials that have gained significant importance in defence,nuclear and aerospace sector due to their superior mechanical properties,heat resistance,high temperature strength and corrosion resistance.These alloys are manufactured by the equal mixing or larger proportions of five or more alloying elements.HEAs exhibit superior mechanical performance compared to traditional engineering alloys because of the extensive alloying composition and higher entropy of mixing.Solid state welding(SSW)techniques such as friction stir welding(FSW),rotary friction welding(RFW),diffusion bonding(DB)and explosive welding(EW)have been efficiently deployed for improving the microstructural integrity and mechanical properties of welded HEA joints.The HEA interlayers revealed greater potential in supressing the formation of deleterious intermetallic phases and maximizing the mechanical properties of HEAs joints.The similar and dissimilar joining of HEAs has been manifested to be viable for HEA systems which further expands their industrial applications.Thus,the main objective of this review paper is to present a critical review of current state of research,challenges and opportunities and main directions in SSW of HEAs mainly CoCrFeNiMn and Al_xCoCrFeNi alloys.The state of the art of problems,progress and future outlook in SSW of HEAs are critically reviewed by considering the formation of phases,microstructural evolution and mechanical properties of HEAs joints.
文摘The effect of Ti addition on microstructure and mechanical properties of Zn-22Al eutectoid alloy with 0.15 wt%Ti was investigated.It was observed that the presence of Ti changes the morphology of n phase in the alloy.Addition of Ti to Zn-Al alloy caused the formation of Ti(Zn,Al)_(3);phase.Before applying equal channel angular pressing(ECAP),two times of homogenization treatment were conducted on the alloy.After secondary homogenization,the microstructure consisted of a homogeneous and fine mixture ofαand n phases and the as-cast lamellar structure removed.After homogenization,ECAP was carried out on Ti-containing Zn-22Al alloy.The fraction of high angle grain boundaries increased with increasing the number of ECAP passes.The average grain size reduced from 930 nm after secondary homogenization to 380 nm after 8 passes of ECAP.The texture of the alloy also changed by applying ECAP.Maximum elongation to failure of the homogenized alloy was 135%at a strain rate of 10^(-5)s^(-1)which enhanced to a maximum of 405%at a strain rate of 10^(-3)s^(-1)after 8 passes of ECAP.It was also observed that by conducting ECAP and increasing the number of passes the hardness decreases,which indicates work-softening behavior due to dynamic recovery/recrystallization.
基金Projects(52274397,52275382)supported by the National Natural Science Foundation of ChinaProject(tsqn202211115)supported by the Taishan Scholars Program of Shandong Province,China+2 种基金Project supported by the Yantai High-end Talent Introduction“Double Hundred Plan”(2021),ChinaProject(ZR2024JQ020)supported by the Shandong Provincial Natural Science Foundation of ChinaProjects(CZ20210034,CM20223013)supported by the Changzhou Sci&Tech Program,China。
文摘In this work,a novel type of short-process deformation technology of Mg alloys,bifurcation-equal channel angular pressing(B-ECAP),was proposed to refine grain and improve the basal texture.The cylindrical billets were first compressed into the die cavity,then sequentially flowed downward through a 90°corner and two 120°shear steps.The total strain of B-ECAP process could reach 3.924 in a single pass.The results of microstructure observation showed that DRX occurred at upsetting process in the die cavity and completed at position D.The grains were refined to 6.3μm at being extruded at 300℃ and grew obviously with the extrusion temperature increase.The shear tress induced by 900 corner and two 120°shear steps resulted in the basal poles of most grains tilted to extrusion direction(ED)by±25°.Compared with the original billets,the extruded sheets exhibited higher yield strengths(YS),which was mainly attributed to the grain refinement.The higher Schmid factor caused by ED-tilt texture resulted in a fracture elongation(FE)more than that of the original bar in ED,while was equivalent to that in transverse direction(TD).As the extrusion temperature increased,the variation of UTS and YS in ED and TD decreased gradually without ductility obviously decrease.
基金Project(202302AB080024)supported by the Department of Science and Technology of Yunnan Province,China。
文摘The evolution of mechanical properties,localized corrosion resistance of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging(NIA)was investigated by hardness test,electrical conductivity test,tensile test,intergranular corrosion test,exfoliation corrosion test,slow strain rate tensile test and electrochemical test,and the mechanism has been discussed based on microstructure examination by optical microscopy,electron back scattered diffraction,scanning electron microscopy and scanning transmission electron microscopy.The NIA treatment includes a heating stage from 40℃to 180℃with a rate of 20℃/h and a cooling stage from 180℃to 40℃with a rate of 10℃/h.The results show that the hardness and strength increase rapidly during the heating stage of NIA since the increasing temperature favors the nucleation and the growth of strengthening precipitates and promotes the transformation of Guinier-Preston(GPI)zones toη'phase.During the cooling stage,the sizes ofη'phase increase with a little change in the number density,leading to a further slight increase of the hardness and strength.As NIA proceeds,the corroded morphology in the alloy changes from a layering feature to a wavy feature,the maximum corrosion depth decreases,and the reason has been analyzed based on the microstructural and microchemical feature of precipitates at grain boundaries and subgrain boundaries.
基金Projects(51935014,82072084,81871498)supported by the Natural Science Foundation of ChinaProjects(20192ACB20005,2020ACB214004)supported by the Jiangxi Provincial Natural Science Foundation of China+4 种基金Project(20201BBE51012)supported by the Provincial Key R&D Projects of Jiangxi Province,ChinaProject(2018)supported by the Guangdong Province Higher Vocational Colleges&Schools Pearl River Scholar Funded Scheme,ChinaProject(2017RS3008)supported by Hunan Provincial Science and Technology Plan,ChinaProject supported by the Open Research Fund of Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology,ChinaProject(2020M682114)China Postdoctoral Science Foundation。
文摘The slow degration of iron limits its bone implant application.The solid solution of Zn in Fe is expected to accelerate the degradation.In this work,mechanical alloying(MA)was used to prepare Fe-Zn powder with supersaturated solid solution.MA significantly decreased the lamellar spacing between particles,thus reducing the diffusion distance of solution atoms.Moreover,it caused a number of crystalline defects,which further promoted the solution diffusion.Subsequently,the MA-processed powder was consolidated into Fe-Zn part by laser sintering,which involved a partial melting/rapid solidification mechanism and retained the original supersaturated solid solution.Results proved that the Fe-Zn alloy became more susceptible with a lowered corrosion potential,and thereby an accelerated corrosion rate of(0.112±0.013)mm/year.Furthermore,it also exhibited favorable cell behavior.This work highlighted the advantage of MA combined with laser sintering for the preparation of Fe-Zn implant with improved degradation performance.
基金Project(202203021221088)supported by the Fundamental Research Program of Shanxi Province,ChinaProject(20230010)supported by the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province,China+5 种基金Project(202201050201012)supported by the Shanxi Provincial Science and Technology Major Special Project Plan of Taking the Lead in Unveiling the List,ChinaProject(2023-063)supported by the Research Project Supported by Shanxi Scholarship Council of ChinaProjects(51771129,52271109)supported by the National Natural Science Foundation of ChinaProject(2021YFB3703300)supported by the National Key Research and Development Program for Young Scientists,ChinaProject(YDZJSX2021B019)supported by the Special Fund Project for Guiding Local Science and Technology Development by the Central Government,ChinaProject(SKL-YSJ202103)supported by the Open Foundation of State Key Laboratory of High-end Compressor and System Technology,China。
文摘In this study,the Mg-3Zn-0.5Zr-χNd(χ=0,0.6)alloys were subjected to final rolling treatment with large deformation of 50%.The impact of annealing temperatures on the microstructure and mechanical properties was investigated.The rolled Mg-3Zn-0.5Zr-0.6Nd alloy exhibited an ultimate tensile strength of 386 MPa,a yield strength of 361 MPa,and an elongation of 7.1%.Annealing at different temperatures resulted in reduced strength and obviously increased elongation for both alloys.Optimal mechanical properties for the Mg-3Zn-0.5Zr-0.6Nd alloy were achieved after annealing at 200℃,with an ultimate tensile strength of 287 MPa,a yield strength of 235 MPa,and an elongation of 26.1%.The numerous deformed microstructures,twins,and precipitated phases in the rolled alloy could impede the deformation at room temperature and increase the work hardening rate.After annealing,a decrease in the work hardening effect and an increase in the dynamic recovery effect were obtained due to the formation of fine equiaxed grains,and the increased volume fraction of precipitated phases,which significantly improved the elongation of the alloy.Additionally,the addition of Nd element could enhance the annealing recrystallization rate,reduce the Schmid factor difference between basal and prismatic slip systems,facilitate multi-system slip initiation and improve the alloy plasticity.
基金Project(2022RALKFKT003)supported by the Open Research Fund from the State Key Laboratory of Rolling and Automation of Northeastern University,ChinaProjects(20232BAB204053,20202ACBL214015)supported by the Natural Science Foundation of Jiangxi Province,China。
文摘In this study,specific warm rolling was carried out to process the Fe_(50)Mn_(30)Co_(10)Cr_(10) high-entropy alloy.The aim was to investigate the effect of warm rolling temperature on the microstructure and mechanical properties.The results indicated that serious transverse cracks appeared in the 25℃ rolled sheet with reduction of 60%,which was significantly improved through 100−300℃ warm rolling.In addition,the increase of rolling temperature promoted dislocation slip and inhibited martensitic transformation and twinning deformation.A single face centered cubic(FCC)matrix with abundant dislocations and stacking faults was developed in the 300℃rolled microstructure.Meanwhile,the deformation stored energy gradually increased,and the copper-type deformation texture was gradually enhanced.After annealing,the recrystallized microstructure of 25−200℃ rolled sheets was composed of FCC and a small amount of HCP phase.However,the hexagonal close packed(HCP)content in the annealed sheet rolled at 300℃ was as high as 20%−23% after annealing for 2−4 min and decreased to 4.5%after annealing for 8 min.All recrystallized microstructure contained a large number of annealing twins,and the average grain size increased with the increase of rolling temperature.Moreover,the mechanical properties of the annealed sheet were significantly improved after warm rolling.
文摘Structural evolution of alloys by ball milling during solid state amorphization were studied by means of XAFS technique. The first one is amorphization process of Fe and B powder mixtures by mechanical alloying (MA), and the second one is amorphization process of ordered B2 CoZr intermetallic compound by mechanical milling (MM). The mixing process of Fe and B and disintegration process of ordered B2 CoZr intermetallic compound crystal were observed clearly in atomic level by XAFS method. The micro mechanism of amorphization process of alloy by ball milling was discussed.
基金Project(50672134) supported by the National Natural Science Foundation of China
文摘Zr50Al15Ni10Cu25 amorphous powder was synthesized by mechanical alloying. The effect of Si3N4 addition on the crystallization behavior of the alloy during sintering process was studied. Thermal stability of the powders was performed by differential scanning calorimetry （DSC）. The phase and microstructure of the powders and bulk specimens sintered were determined by X-ray diffractometry （XRD） and scanning electron microscopy （SEM）. The results show that, introducing 0.05% （mass fraction） Si3N4 can enhance the crystallization activation energy of the ZZr50Al15Ni10Cu25 amorphous powders, which indicates that Si3N4 addition has hindrance effect on forming crystals from Zr50Al15Ni10Cu25amorphous powder. However, 0.10% Si3N4 results in the decrease of the crystallization activation energy, which makes its crystallization process easy to occur.
文摘The mechanical properties and deformation features of AZ31-0.84% Sb alloy have been studied by means of the measurement of the properties and morphology observation. Results show that UTS of AZ31-0.84% Sb alloy at room temperature is 297MPa, a higher value of UTS is still maintained up to 189MPa as temperature elevated to 200℃. One of the main reasons for enhancing UTS of the alloy is attributed to the high volume fraction of the precipitates dispersed in the matrix, including Mg3Sb2 phase, which effectively hindered the movement of dislocations during the elevated temperature deformation. The deformation mechanisms of AZ31-0.84% Sb alloy are the twins and dislocations activated on basal and non-basal planes. a+c dislocations may be activated on the basal and non-basal planes in twins regions, and some of the thinner twins may shear through the dense dislocations within the thicker twins.
基金Project(2012R1A1A1012802) supported by Basic Science Research Program through the National Research Foundation(NRF)of Korea funded by the Ministry of Education,Science and TechnologyProject(2013021013-4) supported by Shanxi Province Science Foundation for Youths,China+1 种基金Project supported by Advanced Programs of Department of Human Resources and Social Security of Shanxi Province for Returned ScholarsProject(2012L003) supported by Foundation for Young Scholars of Taiyuan University of Technology,China
文摘The microstructural evolution and mechanical properties of high speed indirect-extruded Mg-5%Sn-(1, 2, 4) Zn(mass fraction, %) alloys were investigated by optical microscopy(OM), X-ray diffraction(XRD), scanning electron microscopy(SEM), differential thermal analysis(DTA) and a static tension tester. All the studied alloys can be extruded successfully at a high speed of 10 m/min. The grain size, area fraction of particles and tensile properties are found to be greatly affected by the extrusion speed and Zn content, resulting in tensile properties showing lower strength and ductility as the extrusion speed increases and Zn content decreases. The dependence of grain size and tensile properties on the second phase particles is also discussed.
文摘Mechanical properties and tribological behavior of a novel cast heat resisting copper based alloy are investigated. The corresponding properties of a commercial aluminum bronze C95500 (ASTM B30) are compared with the alloy. The results show that the alloy possesses better mechanical properties and tribological behaviors than that of C95500 at elevated temperature. The tensile strength, elongation and hardness at 500℃ are 470MPa, 2.5% and HB220, respectively. The wear rate of the developed alloy at ambient and elevated temperature is about one sixth and one fortieth of that of C95500, respectively. The alloy is very suitable for ma nufacturing heat resisting and wear resisting parts. Major strengthening mechanisms for the alloy are solution strengthening and the second phase strengthening.
基金Project(2019YFB2006500) supported by the National Key Research and Development Program,ChinaProject(51674303) supported by the National Natural Science Foundation of China+3 种基金Project(2020GK2032) supported by Hunan High-tech Industry Science and Technology Innovation Leading Plan,ChinaProject (2018RS3015) supported by the Huxiang High-level Talent Gathering Project of Hunan Province,ChinaProject(2017YFA0700700) supported by the Ministry of Science&Technology of ChinaProject(2019CX006) supported by Innovation Driven Program of Central South University,China。
文摘The mechanical properties and microstructure of Al-Cu-Li alloy sheets subjected to cryorolling(-100 ° C,-190 ℃) or hot rolling(400 ℃) and subsequent aging at 160 ℃ for different times were investigated. The dynamic precipitation and dislocation characterizations were examined via transmission electron microscopy and X-ray diffraction. The grain morphologies and the fracture-surface morphologies were studied via optical microscopy and scanning electron microscopy. Samples subjected to cryorolling followed by aging exhibited relatively high dislocation densities and a large number of precipitates compared with hot-rolled samples. The samples cryorolled at-190 ℃ and then aged for 15 h presented the highest ultimate tensile strength(586 MPa), while the alloy processed via hot rolling followed by 10 h aging exhibited the highest uniform elongation rate(11.5%). The size of precipitates increased with the aging time, which has significant effects on the interaction mechanism between dislocations and precipitates. Bowing is the main interaction method between the deformation-induced dislocations and coarsened precipitates during tensile tests, leading to the decline of the mechanical properties of the alloy during overaging. These interesting findings can provide significant insights into the development of materials possessing both excellent strength and high ductility.
