The effect of hot deformation on the quench sensitivity of the 7085 alloy was studied through hardness testing and microstructure characterization.The findings indicate that hot deformation enhances the quench sensiti...The effect of hot deformation on the quench sensitivity of the 7085 alloy was studied through hardness testing and microstructure characterization.The findings indicate that hot deformation enhances the quench sensitivity of the 7085 alloy,with the hardness difference between water quenching and air cooling increasing from 5.4%(before hot deformation)to 10.4%(after hot deformation).In the undeformed samples,the Al3Zr particles within the grains exhibit better coherent with the Al matrix.During slow quenching,only theηphase is observed on Al3Zr particles and at the grain boundaries.Hot deformation leads to a mass of recrystallization and the formation of subgrains with high dislocation density.This results in an increase in the types,quantities,and sizes of heterogeneous precipitates during quenching.In the slow quenching process,high angle grain boundaries are best for the nucleation and growth of theηphase.Secondly,a substantial quantity ofηand T phases precipitate on the non-coherent Al3Zr phase within the recrystallized grains.The locations with high dislocation density subgrains(boundaries)serve as nucleation positions for theηand T phases precipitating.Additionally,the Y phase is observed to precipitate at dislocation sites within the subgrains.展开更多
The effect of forging on the microstructure and texture evolution of a high Nb containing Ti-45Al-7Nb-0.3W(at.%)alloy was investigated by X-ray diffractometer(XRD),scanning electron microscopy(SEM),and transmission el...The effect of forging on the microstructure and texture evolution of a high Nb containing Ti-45Al-7Nb-0.3W(at.%)alloy was investigated by X-ray diffractometer(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The results show that the as-cast alloy is mainly composed of α_(2)/γ lamellar colonies with a mean size of 70μm,but the hot-forged pancake displays a near duplex microstructure(DP).Kinking and bending of lamellar colonies,deformation twinning and dynamic recrystallization(DRX)occur during hot forging.Meanwhile,dense dislocations in theβphase after forging suggest that the high-temperature β phase with a disordered structure is favorable for improving the hot-workability of the alloy.Unlike the common TiAl casting texture,the solidification process of the investigated as-cast alloy with high Nb content is completely via the β phase region,resulting in the formation of a<110>γ fiber texture where the<110>γ aligns parallel to the heat-flow direction.In comparison,the relatively strong<001>and weak<302>texture components in the as-forged alloy are attributed to the deformation twinning.After annealing,static recrystallization occurs at the twin boundary and intersections,which weakens the deformation texture.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 impact of cooling rate after solution heat treatment on exfoliation corrosion resistance of a Li-containing 7xxx aluminum alloy was investigated by accelerated immersion and electrochemical impedance spectroscopy ...The impact of cooling rate after solution heat treatment on exfoliation corrosion resistance of a Li-containing 7xxx aluminum alloy was investigated by accelerated immersion and electrochemical impedance spectroscopy test,optical microscope,electron backscatter diffraction and scanning transmission electron microscope.With the decrease of cooling rate from 1700℃/s to 4℃/s,exfoliation corrosion resistance of the aged specimens decreases with rating changing from EA to EC and the maximum corrosion depth increasing from about 169.4μm to 632.1μm.Exfoliation corrosion tends to develop along grain boundaries in the specimens with cooling rates higher than about 31℃/s and along both grain boundaries and sub-grain boundaries in the specimens with lower cooling rates.The reason has been discussed based on the changes of the microstructure and microchemistry at grain boundaries and sub-grain boundaries due to slow cooling.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
Ti185 alloy is widely used in key industrial fields such as aerospace due to its excellent mechanical properties.The traditional method of preparing Ti185 alloy will inevitably appear“βfleck”,resulting in the decre...Ti185 alloy is widely used in key industrial fields such as aerospace due to its excellent mechanical properties.The traditional method of preparing Ti185 alloy will inevitably appear“βfleck”,resulting in the decrease of mechanical properties,and the high price of V element limits the wide application of Ti185.In this paper,a low-cost master alloy V-Fe powder is used,a dense block is prepared by spark plasma sintering(SPS)technology,and a high-performance Ti185 alloy is prepared by controlling the sintering parameters.XRD and SEM were used to investigate the phase and microstructure of the samples prepared under different parameters.The compressive strength and friction properties of the directly prepared samples were studied.The samples with a sintering temperature of 1350 ℃ and a holding time of 30 min exhibited the most excellent comprehensive performance,with the highest compressive strength and lowest friction coefficient of 1931.59 MPa and 0.47,respectively.展开更多
Mg–8Li–3Al–0.7Si alloy was prepared by casting and deformed by hot extrusion in this study.And the microstructure of as-cast and extruded specimens was analyzed with OM,XRD,SEM and EDS.Results show that the specime...Mg–8Li–3Al–0.7Si alloy was prepared by casting and deformed by hot extrusion in this study.And the microstructure of as-cast and extruded specimens was analyzed with OM,XRD,SEM and EDS.Results show that the specimens are composed ofα-Mg,β-Li,AlLi,MgLiAl2 and Mg2Si phases.In as-extruded specimen,the microstructure is refined and theβ-Li phase has the effect of coordination during deformation.After hot extrusion,Chinese script Mg2Si phase is crushed into block-like and distributes uniformly in the matrix.Mechanical properties results show that the strength and elongation are both improved after hot extrusion.展开更多
The Al-3.40Mg-1.08Sc alloy plates were manufactured by selective laser melting(SLM) at platform temperatures of 35 ℃ and 200 ℃, respectively, and the corrosion performance of them was studied along height direction....The Al-3.40Mg-1.08Sc alloy plates were manufactured by selective laser melting(SLM) at platform temperatures of 35 ℃ and 200 ℃, respectively, and the corrosion performance of them was studied along height direction. The results show that the corrosion resistance of the alloy plate built at platform temperature of 35 ℃ along height direction is basically the same due to a uniform microstructure;While the corrosion resistance of the alloy plate built at platform temperature of 200 ℃ along height direction is different. The evolution of microstructure and the distribution of secondary phases are investigated, and the results show that the Cu-rich phases in alloy play a key role on corrosion performance. At higher platform temperature, the cooling rate is relative slow and a certain degree of in situ ageing leads to the significantly different distribution of Cu-rich phases along grain boundary. Specimens built at the platform temperature of 200 ℃ are inclined to locate at the crossed grain boundary, rather than continuous segregation of Cu-rich phases along grain boundary that is built at platform temperature of 35 ℃. Therefore, the corrosion resistance of Al-3.40Mg-1.08Sc alloy plate manufactured at platform temperature of 200 ℃ is higher, and presents a gradually decreasing trend along height direction.展开更多
With the microscopic phase-field dynamic model, the effects of temperature and concentration on the nucleation incubation time of Ni75AlxV25-x alloy were studied and the relation between the incubation time and precip...With the microscopic phase-field dynamic model, the effects of temperature and concentration on the nucleation incubation time of Ni75AlxV25-x alloy were studied and the relation between the incubation time and precipitation mechanism was investigated by using the atomic occupation probability picture and average order parameter curve. The simulation results demonstrate that there exists the incubation time for different precipitation mechanisms~ such as non-classical nucleation, the mixed style of non-classical nucleation and spinodal decomposition, and spinodal ordering; and the incubation time shortens in turn for the three kinds of mechanisms. With the increase of Al content of Ni75AlxV25-x alloy, the incubation time of Llz phases shortens continuously and that of DOzz phases is prolonged. The effects of temperature on the incubation time of Llz and DOzz phases are accordant, i.e. the incuba- tion time is greatly prolonged with the temperature rising.展开更多
Massive vanadium additions as hard phases in powder metallurgy high-speed steels(PM HSS)lead to higher cost and bad machinability.In this study,ultrahigh alloy PM HSS with CPM121(10W-5Mo-4Cr-10V-9Co,wt.%)as the basic ...Massive vanadium additions as hard phases in powder metallurgy high-speed steels(PM HSS)lead to higher cost and bad machinability.In this study,ultrahigh alloy PM HSS with CPM121(10W-5Mo-4Cr-10V-9Co,wt.%)as the basic composition,was directly compacted and activation sintered with near-full density(>99.0%)using pre-oxidized and ball-mixed element and carbide powders.Niobium-alloyed steels(w(V)+w(Nb)=10 wt.%)show higher hardness and wear resistance,superior secondary-hardening ability and temper resistance.But excess niobium addition(>5 wt.%)leads to coarsened carbides and deteriorated toughness.EPMA results proved that niobium tends to distribute in MC carbides and forces element W to form M6C and WC carbides.Further,the role of rotary forging on properties of niobium-alloyed steels(S3)was researched.After rotary forging with deformation of 40%,the bending strength and fracture toughness of niobium-alloyed steels could be further improved by 20.74%and 43.86%compared with those of sample S3 without rotary forging,respectively.展开更多
Ultrasonic vibration can reduce the forming force, decrease the friction in the metal forming process and improve the surface quality of the workpiece effectively. Tensile tests of AZ31 magnesium alloy were carried ou...Ultrasonic vibration can reduce the forming force, decrease the friction in the metal forming process and improve the surface quality of the workpiece effectively. Tensile tests of AZ31 magnesium alloy were carried out. The stress–strain relationship, fracture modes of tensile specimens, microstructure and microhardness under different vibration conditions were analyzed, in order to study the effects of the ultrasonic vibration on microstructure and performance of AZ31 magnesium alloy under tensile deformation. The results showed that the different reductions of the true stress appeared under various ultrasonic vibration conditions, and the maximum decreasing range was 4.76%. The maximum microhardness difference among the 3 nodes selected along the specimen was HV 10.9. The fracture modes, plasticity and microstructure of AZ31 magnesium alloy also were affected by amplitude and action time of the ultrasonic vibration. The softening effect and the hardening effect occurred simultaneously when the ultrasonic vibration was applied. When the ultrasonic amplitude was 4.6 μm with short action time, the plastic deformation was dominated by twins and the softening effect was dominant. However, the twinning could be inhibited and the hardening effect became dominant in the case of high ultrasonic energy.展开更多
The microstructures, tensile properties and compressive creep behaviors of Mg-5%Sn-（0-1.0）%Pb （mass fraction） alloys were studied. The microstructures of the Mg-Sn-Pb alloys consist of dendritic a-Mg and Mg2Sn pha...The microstructures, tensile properties and compressive creep behaviors of Mg-5%Sn-（0-1.0）%Pb （mass fraction） alloys were studied. The microstructures of the Mg-Sn-Pb alloys consist of dendritic a-Mg and Mg2Sn phase. The addition of Pb can refine the size of Mg2Sn phase and grain size, reduce the amount of Mg2Sn phase at grain or inter-dendrite boundaries and change the distribution of Mg2Sn phase. Pb exists in the Mg2Sn phase or dissolves in a-Mg matrix. The mechanical properties of the tested alloys at room temperature are improved with the addition of Pb. When the Pb content is over 0.5%, the mechanical properties are decreased gradually. The Mg-5%Sn-0.5%Pb shows the best ultimate tensile strength and elongation, 174 MPa and 14.3%, respectively. However, the compressive creep resistance of the Mg-Sn-Pb alloys is much lower than that of the Mg-Sn binary alloy at 175℃ with applied load of 55 MPa, which means that Pb has negative effects on the compressive creep resistance of the as-cast Mg-Sn alloys.展开更多
As the next generation biomedical titanium alloy, β-type titanium alloys are excellent candidates for biomedical applications due to the relative low elastic modulus and the contained non-toxic elements. However, the...As the next generation biomedical titanium alloy, β-type titanium alloys are excellent candidates for biomedical applications due to the relative low elastic modulus and the contained non-toxic elements. However, the relative low strength and unsatisfactory tribological property are undesired for load-bearing implant applications. In this study, 0-5 at% Si was added to the classic Ti-35Nb-5Ta-7Zr alloy to improve its strength and wear resistance, and the(Ti-35Nb-5Ta-7Zr)1-x-Six(x=0, 1 at% and 5 at%) alloy were fabricated by selective electron beam melting(SEBM)technology. The results indicated that Si addition significantly increases in compressive yield strength, which is mainly due to grain refinement strengthening. At the same time, the wear rate of the as-built TNTZ-5Si alloy in SBF solution was only ~30% of the Ti-6Al-4V alloy. Consequently, the TNTZ-5Si alloy showed an excellent combination of compressive yield strength, elastic modulus and wear resistance for potential load-bearing implant applications.展开更多
Al-Zn-Mg-Sc-Zr alloy samples were annealed to four different states （under-aging, peak-aging, over-aging and double-aging） and then thoroughly investigated by means of electron backscatter diffraction （EBSD）, tran...Al-Zn-Mg-Sc-Zr alloy samples were annealed to four different states （under-aging, peak-aging, over-aging and double-aging） and then thoroughly investigated by means of electron backscatter diffraction （EBSD）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, tensile and fatigue crack growth rate tests to explore the influence of annealing treatment on microstmcture and fatigue crack growth behavior. The results indicate that Al3（Sc,Zr） particles can effectively refine grains and enhance tensile properties and fatigue properties. After annealing treatment, the under-aged sample and double-aged sample obtained average grain sizes of 4.9473 and 4.1257 μm, and the maximum value of yield/tensile strength （561 MPa/581 MPa） was obtained in peak-aged state. In the Paris region, fatigue crack growth rate, crack deflection and bifurcation, crack blunting and inter/trans-granular propagation were discussed based on data fitting and Laird model and Griffith theory. And the results show that the under-aged sample possesses the best resistance to fatigue crack propagation and the most tortuous and bifurcated crack path. For all samples, the fatigue crack growth rate in the rupture region was inversely proportional to yield strength.展开更多
(CrFeCoNi)high-entropy alloy(HEA)was reinforced with various contents of WC particles from 5 wt%to 20 wt%,and prepared by powder metallurgy.The mixed powders were compacted under 700 MPa and then sintered at 1200℃in ...(CrFeCoNi)high-entropy alloy(HEA)was reinforced with various contents of WC particles from 5 wt%to 20 wt%,and prepared by powder metallurgy.The mixed powders were compacted under 700 MPa and then sintered at 1200℃in a vacuum furnace for 90 min.Density,phase composition,and microstructure of sintered samples were investigated.Hardness,compressive strength,wear resistance and coefficient of thermal expansion(CTE)were estimated.The results revealed the improvement of the density with the addition of WC.XRD results revealed the formation of new FCC chromium carbide phases.Scanning electron microscopy(SEM)results show a good distribution of the carbide phases over the alloy matrix.The CTE was decreased gradually by increasing the WC content.Compressive strength was improved by WC addition.A mathematical model was established to predict the behavior of the strength of the HEA samples.The hardness of the investigated HEAs was increased gradually with the increasing of WC content about 20.35%.Also,the wear rate of HEA without WC is 1.70×10^(−4)mm^(3)/(N·m),which is approximately 4.5 times the wear rate of 20 wt%WC HEA(3.81×10^(−5)mm^(3)/(N·m)),which means that wear resistance was significantly improved with the increase of WC content.展开更多
In order to study the corrosion resistance of high-speed laser cladding(HLC) coating while improving production efficiency,a CoCrFeNiMo_(0.2)high-entropy alloy(HEA) coating was prepared by HLC.The optimized parameters...In order to study the corrosion resistance of high-speed laser cladding(HLC) coating while improving production efficiency,a CoCrFeNiMo_(0.2)high-entropy alloy(HEA) coating was prepared by HLC.The optimized parameters of HLC are laser power of 880 W,scanning speed of 18 m/min,overlapping ratio of 60%,and powder feed speed of 3 r/min.Then,the surface roughness,microstructure,phase composition,element distribution,and electrochemical properties in 3.5 wt% NaCl solution of the coatings were analyzed,respectively.The local surface roughness of the CoCrFeNiMo_(0.2)HEA coating was found to be 15.53 μm.A distinct metallurgical bond could be observed between the coating and the substrate.Compared to the conventional laser cladding(CLC),the results of electrochemical tests showed that CoCrFeNiMo_(0.2)HEA coating exhibited a significant passivation.The corrosion current density of 5.4411 × 10^(-6)A·cm^(-2) and the corrosion potential of-0.7445 V for the HLC coating were calculated by the Tafel extrapolation method.The CLC coating’s corrosion current density and corrosion potential are 2.7083×10^(-5)A·cm^(-2) and-0.9685 V,respectively.The HLC coating shows a superior corrosion resistance,crucially due to the uniform and fine grains.Under various complex and harsh working conditions,this method can be widely used in the field of repairing and remanufacturing of corro sion-proof workpiece s.展开更多
Mg-6Al-2Sr alloys with different Sm contents(0%, 0.5%, 1%, 1.5%, 2%, mass fraction) were prepared by melting and casting method. The effects of Sm on the microstructure and mechanical properties of as-cast Mg-6Al-2Sr ...Mg-6Al-2Sr alloys with different Sm contents(0%, 0.5%, 1%, 1.5%, 2%, mass fraction) were prepared by melting and casting method. The effects of Sm on the microstructure and mechanical properties of as-cast Mg-6Al-2Sr alloys were studied by optical microscope, scanning electron microscope, energy dispersive spectrometer, transmission electron microscope, X-ray diffraction and tensile test. The results show that the microstructure of as-cast Mg-6Al-2Sr alloy is composed of α-Mg, Mg_(17)Al_(12), Mg_(13)Al_(3)Sr and lamellar acicular Al_(4)Sr phase. After adding Sm element, granular block Al2Sm phase appears in the grain. With the increase of Sm content, the discontinuous long strip reticular Mg_(17)Al_(12)phase and the lamellar acicular Al4Sr phase gradually decrease, and the Al_(2)Sm phase increases and distributes more dispersedly, so the alloy microstructure is continuously refined. The average grain size of the alloys decreases at first and then increases with the increase of Sm content. When the Sm content is 1.5 wt%, the average grain size reaches the minimum value of 94.6 μm. With the increase of Sm content, the mechanical properties of the alloy at room temperature first increase and then decrease. When the Sm content is 1.5 wt%, the alloy has the best comprehensive mechanical properties at room temperature.展开更多
After a standard heat treatment,the microstructural evolution with time during isothermal aging at 850°C and its effect on the creep rupture properties of the Ni-base superalloy M4706 at 870°C and 370 MPa ar...After a standard heat treatment,the microstructural evolution with time during isothermal aging at 850°C and its effect on the creep rupture properties of the Ni-base superalloy M4706 at 870°C and 370 MPa are investigated.It is found that as the aging time increases from 0 to 5000 h,the average diameter of coarseγ′increases from 241 to 484 nm,and the distribution of the carbides at grain boundaries changes from discontinuous to continuous.Moreover,experimental observations on the microstructures of all the crept specimens reveal that dislocation bypassing controls the creep deformation.Thus,it is concluded that the transitions in the microstructures result in the degeneration of the creep rupture properties of the experimental alloy with aging time.展开更多
Ti-6Al-4V specimens were fabricated by selective laser melting(SLM)to study the effect of thermal treatment on the phase transformation,elemental diffusion,microstructure,and mechanical properties.The results show tha...Ti-6Al-4V specimens were fabricated by selective laser melting(SLM)to study the effect of thermal treatment on the phase transformation,elemental diffusion,microstructure,and mechanical properties.The results show that vanadium enriches around the boundary ofαphases with increasing annealing temperature to 973 K,andα′phases transform intoα+βat 973 K.The typicalα′martensite microstructure transforms to fine-scale equiaxed microstructure at 973 K and the equiaxed microstructure significantly coarsens with increasing annealing temperature to 1273 K.The SLM Ti-6Al-4V alloy annealed at 973 K exhibits a well-balanced combination of strength and ductility((1305±25)MPa and(37±3)%,respectively).展开更多
基金Project(52205421)supported by the National Natural Science Foundation of ChinaProject(AA23023028)supported by the Guangxi Science and Technology Major Project,China+2 种基金Projects(2022B0909070001,2020B010186001)supported by the Key Research and Development Projects of Guangdong Province,ChinaProject(2021B0101220006)supported by the Guangdong Key Areas Research and Development Program“Chip,Software and Computing”Major Project,ChinaProjects(2021RC2087,2022JJ30570)supported by the Science and Technology Innovation Program of Hunan Province,China。
文摘The effect of hot deformation on the quench sensitivity of the 7085 alloy was studied through hardness testing and microstructure characterization.The findings indicate that hot deformation enhances the quench sensitivity of the 7085 alloy,with the hardness difference between water quenching and air cooling increasing from 5.4%(before hot deformation)to 10.4%(after hot deformation).In the undeformed samples,the Al3Zr particles within the grains exhibit better coherent with the Al matrix.During slow quenching,only theηphase is observed on Al3Zr particles and at the grain boundaries.Hot deformation leads to a mass of recrystallization and the formation of subgrains with high dislocation density.This results in an increase in the types,quantities,and sizes of heterogeneous precipitates during quenching.In the slow quenching process,high angle grain boundaries are best for the nucleation and growth of theηphase.Secondly,a substantial quantity ofηand T phases precipitate on the non-coherent Al3Zr phase within the recrystallized grains.The locations with high dislocation density subgrains(boundaries)serve as nucleation positions for theηand T phases precipitating.Additionally,the Y phase is observed to precipitate at dislocation sites within the subgrains.
基金Projects(52274402,52174381)supported by the National Natural Science Foundation of China。
文摘The effect of forging on the microstructure and texture evolution of a high Nb containing Ti-45Al-7Nb-0.3W(at.%)alloy was investigated by X-ray diffractometer(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The results show that the as-cast alloy is mainly composed of α_(2)/γ lamellar colonies with a mean size of 70μm,but the hot-forged pancake displays a near duplex microstructure(DP).Kinking and bending of lamellar colonies,deformation twinning and dynamic recrystallization(DRX)occur during hot forging.Meanwhile,dense dislocations in theβphase after forging suggest that the high-temperature β phase with a disordered structure is favorable for improving the hot-workability of the alloy.Unlike the common TiAl casting texture,the solidification process of the investigated as-cast alloy with high Nb content is completely via the β phase region,resulting in the formation of a<110>γ fiber texture where the<110>γ aligns parallel to the heat-flow direction.In comparison,the relatively strong<001>and weak<302>texture components in the as-forged alloy are attributed to the deformation twinning.After annealing,static recrystallization occurs at the twin boundary and intersections,which weakens the deformation texture.
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 Major Science and Technology Projects of the Science and Technology Department of Yunnan Province,ChinaProject(U21A20130)supported by the National Natural Science Foundation of China。
文摘The impact of cooling rate after solution heat treatment on exfoliation corrosion resistance of a Li-containing 7xxx aluminum alloy was investigated by accelerated immersion and electrochemical impedance spectroscopy test,optical microscope,electron backscatter diffraction and scanning transmission electron microscope.With the decrease of cooling rate from 1700℃/s to 4℃/s,exfoliation corrosion resistance of the aged specimens decreases with rating changing from EA to EC and the maximum corrosion depth increasing from about 169.4μm to 632.1μm.Exfoliation corrosion tends to develop along grain boundaries in the specimens with cooling rates higher than about 31℃/s and along both grain boundaries and sub-grain boundaries in the specimens with lower cooling rates.The reason has been discussed based on the changes of the microstructure and microchemistry at grain boundaries and sub-grain boundaries due to slow cooling.
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Projects(51671152,51874225)supported by the National Natural Science Foundation of ChinaProject(2020ZDLGY13-10)supported by Shaanxi Provincial Science and Technology,China。
文摘Ti185 alloy is widely used in key industrial fields such as aerospace due to its excellent mechanical properties.The traditional method of preparing Ti185 alloy will inevitably appear“βfleck”,resulting in the decrease of mechanical properties,and the high price of V element limits the wide application of Ti185.In this paper,a low-cost master alloy V-Fe powder is used,a dense block is prepared by spark plasma sintering(SPS)technology,and a high-performance Ti185 alloy is prepared by controlling the sintering parameters.XRD and SEM were used to investigate the phase and microstructure of the samples prepared under different parameters.The compressive strength and friction properties of the directly prepared samples were studied.The samples with a sintering temperature of 1350 ℃ and a holding time of 30 min exhibited the most excellent comprehensive performance,with the highest compressive strength and lowest friction coefficient of 1931.59 MPa and 0.47,respectively.
基金Project(51601024)supported by the National Natural Science Foundation,ChinaProjects(2016YFB0700403,2016YFB0301100)supported by the National Key Research and Development Program of China+1 种基金Project(cstc2016jcyj A0418)supported by the Chongqing Research Program of Basic Research and Frontier Technology,ChinaProject(106112016CDJXZ138811)supported by the Fundamental Research Funds for the Central Universities,China
文摘Mg–8Li–3Al–0.7Si alloy was prepared by casting and deformed by hot extrusion in this study.And the microstructure of as-cast and extruded specimens was analyzed with OM,XRD,SEM and EDS.Results show that the specimens are composed ofα-Mg,β-Li,AlLi,MgLiAl2 and Mg2Si phases.In as-extruded specimen,the microstructure is refined and theβ-Li phase has the effect of coordination during deformation.After hot extrusion,Chinese script Mg2Si phase is crushed into block-like and distributes uniformly in the matrix.Mechanical properties results show that the strength and elongation are both improved after hot extrusion.
基金Project(51901207) supported by the National Natural Science Foundation of ChinaProject(2018M632796) supported by the China Postdoctoral Science FoundationProjects(19A430024, 21A430037) supported by the Plan of Henan Key Scientific Research Project of Universities,China。
文摘The Al-3.40Mg-1.08Sc alloy plates were manufactured by selective laser melting(SLM) at platform temperatures of 35 ℃ and 200 ℃, respectively, and the corrosion performance of them was studied along height direction. The results show that the corrosion resistance of the alloy plate built at platform temperature of 35 ℃ along height direction is basically the same due to a uniform microstructure;While the corrosion resistance of the alloy plate built at platform temperature of 200 ℃ along height direction is different. The evolution of microstructure and the distribution of secondary phases are investigated, and the results show that the Cu-rich phases in alloy play a key role on corrosion performance. At higher platform temperature, the cooling rate is relative slow and a certain degree of in situ ageing leads to the significantly different distribution of Cu-rich phases along grain boundary. Specimens built at the platform temperature of 200 ℃ are inclined to locate at the crossed grain boundary, rather than continuous segregation of Cu-rich phases along grain boundary that is built at platform temperature of 35 ℃. Therefore, the corrosion resistance of Al-3.40Mg-1.08Sc alloy plate manufactured at platform temperature of 200 ℃ is higher, and presents a gradually decreasing trend along height direction.
文摘With the microscopic phase-field dynamic model, the effects of temperature and concentration on the nucleation incubation time of Ni75AlxV25-x alloy were studied and the relation between the incubation time and precipitation mechanism was investigated by using the atomic occupation probability picture and average order parameter curve. The simulation results demonstrate that there exists the incubation time for different precipitation mechanisms~ such as non-classical nucleation, the mixed style of non-classical nucleation and spinodal decomposition, and spinodal ordering; and the incubation time shortens in turn for the three kinds of mechanisms. With the increase of Al content of Ni75AlxV25-x alloy, the incubation time of Llz phases shortens continuously and that of DOzz phases is prolonged. The effects of temperature on the incubation time of Llz and DOzz phases are accordant, i.e. the incuba- tion time is greatly prolonged with the temperature rising.
基金Projects(51771237,51704257)supported by the National Natural Science Foundation of ChinaProject(2019JJ60019)supported by the Joint Fund of Hunan Province,ChinaProject(17QDZ25)supported by the School Level Fund of Xiangtan University,China。
文摘Massive vanadium additions as hard phases in powder metallurgy high-speed steels(PM HSS)lead to higher cost and bad machinability.In this study,ultrahigh alloy PM HSS with CPM121(10W-5Mo-4Cr-10V-9Co,wt.%)as the basic composition,was directly compacted and activation sintered with near-full density(>99.0%)using pre-oxidized and ball-mixed element and carbide powders.Niobium-alloyed steels(w(V)+w(Nb)=10 wt.%)show higher hardness and wear resistance,superior secondary-hardening ability and temper resistance.But excess niobium addition(>5 wt.%)leads to coarsened carbides and deteriorated toughness.EPMA results proved that niobium tends to distribute in MC carbides and forces element W to form M6C and WC carbides.Further,the role of rotary forging on properties of niobium-alloyed steels(S3)was researched.After rotary forging with deformation of 40%,the bending strength and fracture toughness of niobium-alloyed steels could be further improved by 20.74%and 43.86%compared with those of sample S3 without rotary forging,respectively.
基金Projects(51375269,51675307) supported by the National Natural Science Foundation of China
文摘Ultrasonic vibration can reduce the forming force, decrease the friction in the metal forming process and improve the surface quality of the workpiece effectively. Tensile tests of AZ31 magnesium alloy were carried out. The stress–strain relationship, fracture modes of tensile specimens, microstructure and microhardness under different vibration conditions were analyzed, in order to study the effects of the ultrasonic vibration on microstructure and performance of AZ31 magnesium alloy under tensile deformation. The results showed that the different reductions of the true stress appeared under various ultrasonic vibration conditions, and the maximum decreasing range was 4.76%. The maximum microhardness difference among the 3 nodes selected along the specimen was HV 10.9. The fracture modes, plasticity and microstructure of AZ31 magnesium alloy also were affected by amplitude and action time of the ultrasonic vibration. The softening effect and the hardening effect occurred simultaneously when the ultrasonic vibration was applied. When the ultrasonic amplitude was 4.6 μm with short action time, the plastic deformation was dominated by twins and the softening effect was dominant. However, the twinning could be inhibited and the hardening effect became dominant in the case of high ultrasonic energy.
基金Project(03GG009-007-4) supported by the Key Program of Science and Technology Bureau of Sichuan Province, China
文摘The microstructures, tensile properties and compressive creep behaviors of Mg-5%Sn-（0-1.0）%Pb （mass fraction） alloys were studied. The microstructures of the Mg-Sn-Pb alloys consist of dendritic a-Mg and Mg2Sn phase. The addition of Pb can refine the size of Mg2Sn phase and grain size, reduce the amount of Mg2Sn phase at grain or inter-dendrite boundaries and change the distribution of Mg2Sn phase. Pb exists in the Mg2Sn phase or dissolves in a-Mg matrix. The mechanical properties of the tested alloys at room temperature are improved with the addition of Pb. When the Pb content is over 0.5%, the mechanical properties are decreased gradually. The Mg-5%Sn-0.5%Pb shows the best ultimate tensile strength and elongation, 174 MPa and 14.3%, respectively. However, the compressive creep resistance of the Mg-Sn-Pb alloys is much lower than that of the Mg-Sn binary alloy at 175℃ with applied load of 55 MPa, which means that Pb has negative effects on the compressive creep resistance of the as-cast Mg-Sn alloys.
基金Project(2019zdzx-04-03) supported by the Science&Technology Specific Projects of Shaanxi Province,ChinaProject(2021KJXX-75) supported by the Innovation Capability Support Plan of Shaanxi Province,China。
文摘As the next generation biomedical titanium alloy, β-type titanium alloys are excellent candidates for biomedical applications due to the relative low elastic modulus and the contained non-toxic elements. However, the relative low strength and unsatisfactory tribological property are undesired for load-bearing implant applications. In this study, 0-5 at% Si was added to the classic Ti-35Nb-5Ta-7Zr alloy to improve its strength and wear resistance, and the(Ti-35Nb-5Ta-7Zr)1-x-Six(x=0, 1 at% and 5 at%) alloy were fabricated by selective electron beam melting(SEBM)technology. The results indicated that Si addition significantly increases in compressive yield strength, which is mainly due to grain refinement strengthening. At the same time, the wear rate of the as-built TNTZ-5Si alloy in SBF solution was only ~30% of the Ti-6Al-4V alloy. Consequently, the TNTZ-5Si alloy showed an excellent combination of compressive yield strength, elastic modulus and wear resistance for potential load-bearing implant applications.
基金Project(2012CB691503)supported by the National Key Basic Research and Development Program of ChinaProject(2016B090931001)supported by Science and Technology Program of Guangdong Province,China
文摘Al-Zn-Mg-Sc-Zr alloy samples were annealed to four different states （under-aging, peak-aging, over-aging and double-aging） and then thoroughly investigated by means of electron backscatter diffraction （EBSD）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, tensile and fatigue crack growth rate tests to explore the influence of annealing treatment on microstmcture and fatigue crack growth behavior. The results indicate that Al3（Sc,Zr） particles can effectively refine grains and enhance tensile properties and fatigue properties. After annealing treatment, the under-aged sample and double-aged sample obtained average grain sizes of 4.9473 and 4.1257 μm, and the maximum value of yield/tensile strength （561 MPa/581 MPa） was obtained in peak-aged state. In the Paris region, fatigue crack growth rate, crack deflection and bifurcation, crack blunting and inter/trans-granular propagation were discussed based on data fitting and Laird model and Griffith theory. And the results show that the under-aged sample possesses the best resistance to fatigue crack propagation and the most tortuous and bifurcated crack path. For all samples, the fatigue crack growth rate in the rupture region was inversely proportional to yield strength.
文摘(CrFeCoNi)high-entropy alloy(HEA)was reinforced with various contents of WC particles from 5 wt%to 20 wt%,and prepared by powder metallurgy.The mixed powders were compacted under 700 MPa and then sintered at 1200℃in a vacuum furnace for 90 min.Density,phase composition,and microstructure of sintered samples were investigated.Hardness,compressive strength,wear resistance and coefficient of thermal expansion(CTE)were estimated.The results revealed the improvement of the density with the addition of WC.XRD results revealed the formation of new FCC chromium carbide phases.Scanning electron microscopy(SEM)results show a good distribution of the carbide phases over the alloy matrix.The CTE was decreased gradually by increasing the WC content.Compressive strength was improved by WC addition.A mathematical model was established to predict the behavior of the strength of the HEA samples.The hardness of the investigated HEAs was increased gradually with the increasing of WC content about 20.35%.Also,the wear rate of HEA without WC is 1.70×10^(−4)mm^(3)/(N·m),which is approximately 4.5 times the wear rate of 20 wt%WC HEA(3.81×10^(−5)mm^(3)/(N·m)),which means that wear resistance was significantly improved with the increase of WC content.
基金Project(2020E0264) supported by the Xinjiang Science and Technology Project Plan of Autonomous Region,ChinaProject(2020D01C030) supported by the Autonomous Region Natural Science Foundation,China。
文摘In order to study the corrosion resistance of high-speed laser cladding(HLC) coating while improving production efficiency,a CoCrFeNiMo_(0.2)high-entropy alloy(HEA) coating was prepared by HLC.The optimized parameters of HLC are laser power of 880 W,scanning speed of 18 m/min,overlapping ratio of 60%,and powder feed speed of 3 r/min.Then,the surface roughness,microstructure,phase composition,element distribution,and electrochemical properties in 3.5 wt% NaCl solution of the coatings were analyzed,respectively.The local surface roughness of the CoCrFeNiMo_(0.2)HEA coating was found to be 15.53 μm.A distinct metallurgical bond could be observed between the coating and the substrate.Compared to the conventional laser cladding(CLC),the results of electrochemical tests showed that CoCrFeNiMo_(0.2)HEA coating exhibited a significant passivation.The corrosion current density of 5.4411 × 10^(-6)A·cm^(-2) and the corrosion potential of-0.7445 V for the HLC coating were calculated by the Tafel extrapolation method.The CLC coating’s corrosion current density and corrosion potential are 2.7083×10^(-5)A·cm^(-2) and-0.9685 V,respectively.The HLC coating shows a superior corrosion resistance,crucially due to the uniform and fine grains.Under various complex and harsh working conditions,this method can be widely used in the field of repairing and remanufacturing of corro sion-proof workpiece s.
基金Project(51975167) supported by the National Natural Science Foundation,China。
文摘Mg-6Al-2Sr alloys with different Sm contents(0%, 0.5%, 1%, 1.5%, 2%, mass fraction) were prepared by melting and casting method. The effects of Sm on the microstructure and mechanical properties of as-cast Mg-6Al-2Sr alloys were studied by optical microscope, scanning electron microscope, energy dispersive spectrometer, transmission electron microscope, X-ray diffraction and tensile test. The results show that the microstructure of as-cast Mg-6Al-2Sr alloy is composed of α-Mg, Mg_(17)Al_(12), Mg_(13)Al_(3)Sr and lamellar acicular Al_(4)Sr phase. After adding Sm element, granular block Al2Sm phase appears in the grain. With the increase of Sm content, the discontinuous long strip reticular Mg_(17)Al_(12)phase and the lamellar acicular Al4Sr phase gradually decrease, and the Al_(2)Sm phase increases and distributes more dispersedly, so the alloy microstructure is continuously refined. The average grain size of the alloys decreases at first and then increases with the increase of Sm content. When the Sm content is 1.5 wt%, the average grain size reaches the minimum value of 94.6 μm. With the increase of Sm content, the mechanical properties of the alloy at room temperature first increase and then decrease. When the Sm content is 1.5 wt%, the alloy has the best comprehensive mechanical properties at room temperature.
基金Project(2018BSHQYXMZZ32)supported by the Postdoctoral Science Foundation of Shaanxi Province of ChinaProject(20192109)supported by the State Key Laboratory for Mechanical Behavior of Materials,ChinaProjects(2017M623213,2018M633487)supported by the Postdoctoral Science Foundation of China
文摘After a standard heat treatment,the microstructural evolution with time during isothermal aging at 850°C and its effect on the creep rupture properties of the Ni-base superalloy M4706 at 870°C and 370 MPa are investigated.It is found that as the aging time increases from 0 to 5000 h,the average diameter of coarseγ′increases from 241 to 484 nm,and the distribution of the carbides at grain boundaries changes from discontinuous to continuous.Moreover,experimental observations on the microstructures of all the crept specimens reveal that dislocation bypassing controls the creep deformation.Thus,it is concluded that the transitions in the microstructures result in the degeneration of the creep rupture properties of the experimental alloy with aging time.
基金Project(2020A1515110869)supported by Guangdong Basic and Applied Basic Research Foundation,ChinaProject(GJHZ20190822095418365)supported by Shenzhen International Cooperation Research,China+3 种基金Project(51775351)supported by the National Natural Science Foundation of ChinaProject(2019011)supported by the NTUT-SZU Joint Research Program,ChinaProject(2019040)supported by the Natural Science Foundation of SZU,ChinaProject(ASTRA6-6)supported by the European Regional Development Fund,European Union。
文摘Ti-6Al-4V specimens were fabricated by selective laser melting(SLM)to study the effect of thermal treatment on the phase transformation,elemental diffusion,microstructure,and mechanical properties.The results show that vanadium enriches around the boundary ofαphases with increasing annealing temperature to 973 K,andα′phases transform intoα+βat 973 K.The typicalα′martensite microstructure transforms to fine-scale equiaxed microstructure at 973 K and the equiaxed microstructure significantly coarsens with increasing annealing temperature to 1273 K.The SLM Ti-6Al-4V alloy annealed at 973 K exhibits a well-balanced combination of strength and ductility((1305±25)MPa and(37±3)%,respectively).
