Titanium alloy has the advantages of high strength,strong corrosion resistance,excellent high and low temperature mechanical properties,etc.,and is widely used in aerospace,shipbuilding,weapons and equipment,and other...Titanium alloy has the advantages of high strength,strong corrosion resistance,excellent high and low temperature mechanical properties,etc.,and is widely used in aerospace,shipbuilding,weapons and equipment,and other fields.In recent years,with the continuous increase in demand for medium-thick plate titanium alloys,corresponding welding technologies have also continued to develop.Therefore,this article reviews the research progress of deep penetration welding technology for medium-thick plate titanium alloys,mainly covering traditional arc welding,high-energy beam welding,and other welding technologies.Among many methods,narrow gap welding,hybrid welding,and external energy field assistance welding all contribute to improving the welding efficiency and quality of medium-thick plate titanium alloys.Finally,the development trend of deep penetration welding technology for mediumthick plate titanium alloys is prospected.展开更多
High-entropy alloys(HEAs)have become essential materials in the aerospace and defense industries due to their remarkable mechanical properties,which include wear resistance,fatigue endurance,and corrosion resistance.T...High-entropy alloys(HEAs)have become essential materials in the aerospace and defense industries due to their remarkable mechanical properties,which include wear resistance,fatigue endurance,and corrosion resistance.The welding of high-entropy alloys is a cutting-edge field of study that is attracting a lot of interest and investigation from research organizations and businesses.Welding defects including porosity and cracks are challenging problem and limit the development of welding HEAs.This paper provides a comprehensive review of research on weldability of HEAs and the application of diverse welding techniques on welding HEAs over recent years.The forming mechanism and control strategies of defects during welding HEAs were provided in this work.Various welding techniques,including arc welding,laser welding,electron beam welding,friction stir welding,diffusion bonding and explosive welding,have been extensively investigated and applied to improve the microstructure and mechanical properties of HEAs joints.Furthermore,an in-depth review of the microstructure and mechanical properties of HEAs joints obtained by various welding methods is presented.This paper concludes with a discussion of the potential challenges associated with high-entropy alloy welding,thus providing valuable insights for future research efforts in this area.展开更多
This study proposes a general imperfect thermal contact model to predict the thermal contact resistance at the interface among multi-layered composite structures.Based on the Green-Lindsay(GL)thermoelastic theory,semi...This study proposes a general imperfect thermal contact model to predict the thermal contact resistance at the interface among multi-layered composite structures.Based on the Green-Lindsay(GL)thermoelastic theory,semi analytical solutions of temperature increment and displacement of multi-layered composite structures are obtained by using the Laplace transform method,upon which the effects of thermal resistance coefficient,partition coefficient,thermal conductivity ratio and heat capacity ratio on the responses are studied.The results show that the generalized imperfect thermal contact model can realistically describe the imperfect thermal contact problem.Accordingly,it may degenerate into other thermal contact models by adjusting the thermal resistance coefficient and partition coefficient.展开更多
Stab-resistant textiles play a critical role in personal protection,necessitating a deeper understanding of how structural and layering factors influence their performance.The current study experimentally examines the...Stab-resistant textiles play a critical role in personal protection,necessitating a deeper understanding of how structural and layering factors influence their performance.The current study experimentally examines the effects of textile structure,layering,and ply orientation on the stab resistance of multi-layer textiles.Three 3D warp interlock(3DWI)structures({f1},{f2},{f3})and a 2D woven fabric({f4}),all made of high-performance p-aramid yarns,were engineered and manufactured.Multi-layer specimens were prepared and subjected to drop-weight stabbing tests following HOSBD standards.Stabbing performance metrics,including Depth of Trauma(DoT),Depth of Penetration(DoP),and trauma deformation(Ymax,Xmax),were investigated and analyzed.Statistical analyses(Two-and One-Way ANOVA)indicated that fabric type and layer number significantly impacted DoP(P<0.05),while ply orientation significantly affected DoP(P<0.05)but not DoT(P>0.05).Further detailed analysis revealed that 2D woven fabrics exhibited greater trauma deformation than 3D WIF structures.Increasing the number of layers reduced both DoP and DoT across all fabric structures,with f3 demonstrating the best performance in multi-layer configurations.Aligned ply orientations also enhanced stab resistance,underscoring the importance of alignment in dissipating impact energy.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
By considering the joint effects of the Kelvin-Helmholtz(KH) and Rayleigh-Taylor(RT) instabilities, this paper presents an interpretation of the wavy patterns that occur in explosive welding. It is assumed that the el...By considering the joint effects of the Kelvin-Helmholtz(KH) and Rayleigh-Taylor(RT) instabilities, this paper presents an interpretation of the wavy patterns that occur in explosive welding. It is assumed that the elasticity of the material at the interface effectively determines the wavelength, because explosive welding is basically a solid-state welding process. To this end, an analytical model of elastic hydrodynamic instabilities is proposed, and the most unstable mode is selected in the solid phase. Similar approaches have been widely used to study the interfacial behavior of solid metals in high-energy-density physics. By comparing the experimental and theoretical results, it is concluded that thermal softening,which significantly reduces the shear modulus, is necessary and sufficient for successful welding. The thermal softening is verified by theoretical analysis of the increase in temperature due to the impacting and sliding of the flyer and base plates, and some experimental observations are qualitatively validated.In summary, the combined effect of the KH and RT instabilities in solids determines the wavy morphology, and our theoretical results are in good qualitative agreement with experimental and numerical observations.展开更多
This study investigates the corrosion-assisted fatigue crack growth rate(FCGR)of 16 mm thick AA 7075-T651 friction stir welded(FSW)joints.Compact tension(CT)specimens were extracted from both the base material and FSW...This study investigates the corrosion-assisted fatigue crack growth rate(FCGR)of 16 mm thick AA 7075-T651 friction stir welded(FSW)joints.Compact tension(CT)specimens were extracted from both the base material and FSW joints to evaluate FCGR under varying corrosion exposure durations(0,7,30,60,and 90 days)at a constant stress ratio of 0.5.Microstructural analysis of the welds was conducted using optical and transmission electron microscopy(TEM).Results indicate that the critical stress intensity factor range(ΔK_(cr))of FSW joints is lower than that of the base material,primarily due to precipitate dissolution in the weld zone during the FSW process,as confirmed by TEM analysis.The fatigue life of FSW joints was significantly lower than that of the base material,but with prolonged exposure to seawater corrosion,the gap in fatigue life narrowed.Specimens exposed to seawater for more than 60days exhibited minimal differences in fatigue life between the base material and the FSW joints.This was attributed to the higher corrosion rate of the base material compared to the weld nugget,resulting in the formation of deeper pits that facilitated crack initiation and accelerated fatigue failure.The findings conclude that extended corrosion exposure leads to similar fatigue life and crack growth behaviour in both the base material and FSW joints.SEM and EDX analysis of AA7075-T651 revealed corrosion pits and rust products in initiation zones,ductile striations in growth regions,and secondary cracks with micro voids in fracture zones.FSW joints exhibited ultra-fine grains,smooth ductile fracture in initiation and growth regions,and brittle fracture in the fracture zones under both corroded and uncorroded conditions.展开更多
This study examines the effects of friction stir welding(FSW)and post-weld heat treatment(PWHT)on the grain boundary character distribution and corrosion resistance of cross sectional(top and bottom)regions of nickel-...This study examines the effects of friction stir welding(FSW)and post-weld heat treatment(PWHT)on the grain boundary character distribution and corrosion resistance of cross sectional(top and bottom)regions of nickel-and molybdenum-free high-nitrogen austenitic stainless steel(HNASS).FSW at 400 rpm and 30 mm/min resulted in finer grains(4.18μm)and higher coincident site lattice(CSL)boundaries(32.3%)at the top of the stir zone(SZ)due to dynamic recrystallization(DRX).PWHT at 900℃for 1 h led to grain coarsening(12.91μm the bottom SZ)but enhanced CSL boundaries from 24.6%to 30.2%,improving grain boundary stability.PWHT reduced the kernel average misorientation(KAM)by 14.9%in the SZ-top layer and 20.4%in the SZ-bottom layer,accompanied by a 25%decrease in hardness in the SZ-top layer and 26.7%in the SZ-bottom layer,indicating strain recovery and reduced dislocation density.Potentiodynamic polarization tests(PDP)showed a 18%increase in pitting potential and a 76%reduction in corrosion rate after PWHT.The improvement in corrosion resistance is attributed to the increase inΣ3 twin boundaries,which enhance grain boundary stability and reduce susceptibility to localized corrosion.These findings highlight the role of PWHT in refining the microstructure and strengthening corrosion resistance,making HNASS a promising material for demanding applications.展开更多
Al-Mg-Mn-Sc-Zr alloys with excellent weldability have emerged as ideal candidates for aerospace applications.Currently,the investigations on the corrosion behavior of alloys under tungsten inert gas(TIG)welding condit...Al-Mg-Mn-Sc-Zr alloys with excellent weldability have emerged as ideal candidates for aerospace applications.Currently,the investigations on the corrosion behavior of alloys under tungsten inert gas(TIG)welding conditions are insufficient.Here,the stress corrosion cracking(SCC)behavior of base metal(BM)and weld zone(WZ)of TIG welded Al-Mg-Mn-Sc-Zr alloys was investigated by using pre-cracked compact tensile samples immersed in 3.5%NaCl solution.The direct current potential drop(DCPD)method was used to record the crack propagation.The microstructure and fracture morphology of different regions of TIG welded joints were studied by SEM,EBSD and TEM,and the SCC crack propagation mechanism of BM and WZ was analyzed.The results demonstrated that the critical stress intensity factor for stress corrosion cracking(K_(ⅠSCC))of BM and WZ was 7.05 MPa·m_(1/2) and 11.79 MPa·m_(1/2),respectively.Then,the crack propagation rate of BM was faster than that of WZ,and BM was more susceptible to SCC than WZ.Additionally,the fracture mode of the BM mainly exhibited transgranular fracture,while the fracture mode of the WZ mainly exhibited intergranular and transgranular mixed fracture.Moreover,SCC crack propagation was attributed to the combined effect of anodic dissolution and hydrogen embrittlement.This study will provide experimental and theoretical basis for the wide application of TIG welded Al-Mg-Mn-Sc-Zr alloys in aerospace.展开更多
High nitrogen stainless steel(HNS) is a nickel free austenitic stainless steel that is used as a structural component in defence applications for manufacturing battle tanks as a replacement of the existing armour grad...High nitrogen stainless steel(HNS) is a nickel free austenitic stainless steel that is used as a structural component in defence applications for manufacturing battle tanks as a replacement of the existing armour grade steel owing to its low cost, excellent mechanical properties and better corrosion resistance.Conventional fusion welding causes problems like nitrogen desorption, solidification cracking in weld zone, liquation cracking in heat affected zone, nitrogen induced porosity and poor mechanical properties.The above problems can be overcome by proper selection and procedure of joining process. In the present work, an attempt has been made to correlate the microstructural changes with mechanical properties of fusion and solid state welds of high nitrogen steel. Shielded metal arc welding(SMAW), gas tungsten arc welding(GTAW), electron beam welding(EBW) and friction stir welding(FSW) processes were used in the present work. Optical microscopy, scanning electron microscopy and electron backscatter diffraction were used to characterize microstructural changes. Hardness, tensile and bend tests were performed to evaluate the mechanical properties of welds. The results of the present investigation established that fully austenitic dendritic structure was found in welds of SMAW. Reverted austenite pools in the martensite matrix in weld zone and unmixed zones near the fusion boundary were observed in GTA welds. Discontinuous ferrite network in austenite matrix was observed in electron beam welds.Fine recrystallized austenite grain structure was observed in the nugget zone of friction stir welds.Improved mechanical properties are obtained in friction stir welds when compared to fusion welds. This is attributed to the refined microstructure consisting of equiaxed and homogenous austenite grains.展开更多
AA5059 is one of the high strength armor grade aluminium alloy that finds its applications in the military vehicles due to the higher resistance against the armor piercing (AP) threats. This study aimed at finding the...AA5059 is one of the high strength armor grade aluminium alloy that finds its applications in the military vehicles due to the higher resistance against the armor piercing (AP) threats. This study aimed at finding the best suitable process among the fusion welding processes such as gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) by evaluating the tensile properties of AA5059 aluminium alloy joints. The fracture path was identified by mapping the low hardness distribution profile (LHDP) across the weld cross section under tensile loading. Optical and scanning electron microscopies were used to characterize the microstructural features of the welded joints at various zones. It is evident from the results that GTAW joints showed superior tensile properties compared to GMAW joints and this is primarily owing to the presence of finer grains in the weld metal zone (WMZ) and narrow heat-affected zone (HAZ). The lower heat input associated with the GTAW process effectively reduced the size of the WMZ and HAZ compared to GMAW process. Lower heat input of GTAW process results in faster cooling rate which hinders the grain growth and reduces the evaporation of magnesium in weld metal compared to GMAW joints. The fracture surface of GTAW joint consists of more dimples than GMAW joints which is an indication that the GTAW joint possess improved ductility than GMAW joint.展开更多
Friction stir welding(FSW) is a promising welding process that can join age hardenable aluminium alloys with high joint efficiency. However,the thermal cycles experienced by the material to be joined during FSW result...Friction stir welding(FSW) is a promising welding process that can join age hardenable aluminium alloys with high joint efficiency. However,the thermal cycles experienced by the material to be joined during FSW resulted in the deterioration of mechanical properties due to the coarsening and dissolution of strengthening precipitates in the thermo-mechanical affected zone(TMAZ) and heat affected zone(HAZ). Under water friction stir welding(UWFSW) is a variant of FSW process which can maintain low heat input as well as constant heat input along the weld line. The heat conduction and dissipation during UWFSW controls the width of TMAZ and HAZ and also improves the joint properties. In this investigation, an attempt has been made to evaluate the mechanical properties and microstructural characteristics of AA2519-T87 aluminium alloy joints made by FSW and UWFSW processes. Finite element analysis has been used to estimate the temperature distribution and width of TMAZ region in both the joints and the results have been compared with experimental results and subsequently correlated with mechanical properties.? 2016 China Ordnance Society. Production and hosting by Elsevier B.V. All rights reserved.展开更多
Submerged arc welding(SAW), owing to its high deposition rate and high welding quality, is widely used in the fabrication of pressure vessel, marine vessel, pipelines and offshore structures. However, selection of an ...Submerged arc welding(SAW), owing to its high deposition rate and high welding quality, is widely used in the fabrication of pressure vessel, marine vessel, pipelines and offshore structures. However, selection of an optimum combination of welding parameters is critical in achieving high weld quality and productivity. In this work, initially, the SAW experiments were performed using fractional factorial design to analyze the effect of direct and indirect input parameters, namely, welding voltage, wire feed rate,welding speed, nozzle to plate distance, flux condition, and plate thickness on weld bead geometrical responses viz. bead width, reinforcement, and penetration. The bead on plate technique was used to deposit weld metal on AISI 1023 steel plates. The effect of SAW input parameters on response variables were analyzed using main and interaction effects. The linear regression was used to develop the mathematical models for the response variable. Then, the multi-objective optimization of input parameters was carried out using desirability approach, genetic algorithm and Jaya algorithm. The Jaya algorithm offered better optimization results as compared to desirability approach, genetic algorithm.展开更多
The activated TIG(ATIG) welding process mainly focuses on increasing the depth of penetration and the reduction in the width of weld bead has not been paid much attention.The shape of a weld in terms of its width-to-d...The activated TIG(ATIG) welding process mainly focuses on increasing the depth of penetration and the reduction in the width of weld bead has not been paid much attention.The shape of a weld in terms of its width-to-depth ratio known as aspect ratio has a marked influence on its solidification cracking tendency.The major influencing ATIG welding parameters,such as electrode gap,travel speed,current and voltage,that aid in controlling the aspect ratio of DSS joints,must be optimized to obtain desirable aspect ratio for DSS joints.Hence in this study,the above parameters of ATIG welding for aspect ratio of ASTM/UNS S32205 DSS welds are optimized by using Taguchi orthogonal array(OA)experimental design and other statistical tools such as Analysis of Variance(ANOVA) and Pooled ANOVA techniques.The optimum process parameters are found to be 1 mm electrode gap,130 mm/min travel speed,140 A current and 12 V voltage.The aspect ratio and the ferrite content for the DSS joints fabricated using the optimized ATIG parameters are found to be well within the acceptable range and there is no macroscopically evident solidification cracking.展开更多
Bead-on-plate friction stir welds were made on P91 alloy with low and high rotational speeds(100 and 1000 RPM) to study their effects on weld microstructural changes and impression creep behavior. Temperatures experie...Bead-on-plate friction stir welds were made on P91 alloy with low and high rotational speeds(100 and 1000 RPM) to study their effects on weld microstructural changes and impression creep behavior. Temperatures experienced by the stir zone were recorded at the weld tool tip. Different zones of welds were characterized for their microstructural changes, hardness and creep behavior(by impression creep tests). The results were compared with submerged arc fusion weld. Studies revealed that the stir zone temperature with 100 RPM was well below A_(c1) temperature of P91 steel while it was above A_(c3) with 1000 RPM. The results suggest that the microstructural degradation in P91 welds can be controlled by low temperature friction stir welding technique.展开更多
Three different kinds of PELE(the penetrator with lateral efficiency) were launched by ballistic artillery to impact the multi-layer spaced metal target plates.The lmpact velocities of the projectiles were measured by...Three different kinds of PELE(the penetrator with lateral efficiency) were launched by ballistic artillery to impact the multi-layer spaced metal target plates.The lmpact velocities of the projectiles were measured by the velocity measuring system.The damage degree and process of each laye r of target plate impacted by the three kinds of projectiles were analyzed.The experimental results show that all the three kinds of projectiles have the effect of expanding holes on the multi-layer spaced metal target plates.For the normal structure PELE(without layered) with tungsten alloy jacket and the radial layered PELE with tungsten alloy jacket,the diameters of holes on the seco nd layer of plates are 3.36 times and 3.76 times of the diameter of the projectile,re spectively.For radial layered PELE with W/Zr-based amorphous composite jacket,due to the large number of tungsten wires dispersed after the impact,the diameter of the holes on the four-layer spaced plates can reach 2.4 times,3.04 times,5.36 times and 2.68 times of the diameter of the projectile.Besides,the normal structure PELE with tungsten alloy jacket and the radial layered PELE whit tungsten alloy jacket formed a large number of fragments impact marks on the third target plate.Although the number of fragments penetrating the third target plate is not as large as that of the normal structure PELE,the area of dispersion of fragments impact craters on the third target plate is larger by the radial layered PELE.The radial layered PELE with W/Zr-based amorphous composite jacket released a lot of heat energy due to the impact of the matrix material,and formed a large area of ablation marks on the last three target plates.展开更多
基金financially supported by the Key Research and Development Program of Ningbo(Grant No.2023Z098)Natural Science Foundation of Inner Mongolia(Grant No.2023MS05040)+1 种基金Shenyang Collaborative Innovation Center Project for Multiple Energy Fields Composite Processing of Special Materials(Grant No.JG210027)Shenyang Key Technology Special Project of The Open Competition Mechanism to Select the Best Solution(Grant Nos.2022210101000827,2022-0-43-048).
文摘Titanium alloy has the advantages of high strength,strong corrosion resistance,excellent high and low temperature mechanical properties,etc.,and is widely used in aerospace,shipbuilding,weapons and equipment,and other fields.In recent years,with the continuous increase in demand for medium-thick plate titanium alloys,corresponding welding technologies have also continued to develop.Therefore,this article reviews the research progress of deep penetration welding technology for medium-thick plate titanium alloys,mainly covering traditional arc welding,high-energy beam welding,and other welding technologies.Among many methods,narrow gap welding,hybrid welding,and external energy field assistance welding all contribute to improving the welding efficiency and quality of medium-thick plate titanium alloys.Finally,the development trend of deep penetration welding technology for mediumthick plate titanium alloys is prospected.
基金Project(52105351)supported by the National Natural Science Foundation of ChinaProject(24KJA460002)supported by the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province,ChinaProject(G2023014009L)supported by the High-end Foreign Experts Recruitment Plan of China。
文摘High-entropy alloys(HEAs)have become essential materials in the aerospace and defense industries due to their remarkable mechanical properties,which include wear resistance,fatigue endurance,and corrosion resistance.The welding of high-entropy alloys is a cutting-edge field of study that is attracting a lot of interest and investigation from research organizations and businesses.Welding defects including porosity and cracks are challenging problem and limit the development of welding HEAs.This paper provides a comprehensive review of research on weldability of HEAs and the application of diverse welding techniques on welding HEAs over recent years.The forming mechanism and control strategies of defects during welding HEAs were provided in this work.Various welding techniques,including arc welding,laser welding,electron beam welding,friction stir welding,diffusion bonding and explosive welding,have been extensively investigated and applied to improve the microstructure and mechanical properties of HEAs joints.Furthermore,an in-depth review of the microstructure and mechanical properties of HEAs joints obtained by various welding methods is presented.This paper concludes with a discussion of the potential challenges associated with high-entropy alloy welding,thus providing valuable insights for future research efforts in this area.
基金Projects(42477162,52108347,52178371,52168046,52178321,52308383)supported by the National Natural Science Foundation of ChinaProjects(2023C03143,2022C01099,2024C01219,2022C03151)supported by the Zhejiang Key Research and Development Plan,China+6 种基金Project(LQ22E080010)supported by the Exploring Youth Project of Zhejiang Natural Science Foundation,ChinaProject(LR21E080005)supported by the Outstanding Youth Project of Natural Science Foundation of Zhejiang Province,ChinaProject(2022M712964)supported by the Postdoctoral Science Foundation of ChinaProject(2023AFB008)supported by the Natural Science Foundation of Hubei Province for Youth,ChinaProject(202203)supported by Engineering Research Centre of Rock-Soil Drilling&Excavation and Protection,Ministry of Education,ChinaProject(202305-2)supported by the Science and Technology Project of Zhejiang Provincial Communication Department,ChinaProject(2021K256)supported by the Construction Research Founds of Department of Housing and Urban-Rural Development of Zhejiang Province,China。
文摘This study proposes a general imperfect thermal contact model to predict the thermal contact resistance at the interface among multi-layered composite structures.Based on the Green-Lindsay(GL)thermoelastic theory,semi analytical solutions of temperature increment and displacement of multi-layered composite structures are obtained by using the Laplace transform method,upon which the effects of thermal resistance coefficient,partition coefficient,thermal conductivity ratio and heat capacity ratio on the responses are studied.The results show that the generalized imperfect thermal contact model can realistically describe the imperfect thermal contact problem.Accordingly,it may degenerate into other thermal contact models by adjusting the thermal resistance coefficient and partition coefficient.
文摘Stab-resistant textiles play a critical role in personal protection,necessitating a deeper understanding of how structural and layering factors influence their performance.The current study experimentally examines the effects of textile structure,layering,and ply orientation on the stab resistance of multi-layer textiles.Three 3D warp interlock(3DWI)structures({f1},{f2},{f3})and a 2D woven fabric({f4}),all made of high-performance p-aramid yarns,were engineered and manufactured.Multi-layer specimens were prepared and subjected to drop-weight stabbing tests following HOSBD standards.Stabbing performance metrics,including Depth of Trauma(DoT),Depth of Penetration(DoP),and trauma deformation(Ymax,Xmax),were investigated and analyzed.Statistical analyses(Two-and One-Way ANOVA)indicated that fabric type and layer number significantly impacted DoP(P<0.05),while ply orientation significantly affected DoP(P<0.05)but not DoT(P>0.05).Further detailed analysis revealed that 2D woven fabrics exhibited greater trauma deformation than 3D WIF structures.Increasing the number of layers reduced both DoP and DoT across all fabric structures,with f3 demonstrating the best performance in multi-layer configurations.Aligned ply orientations also enhanced stab resistance,underscoring the importance of alignment in dissipating impact energy.
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.
基金the National Natural Science Foundation of China(Grant Nos.12002037 and 12141201).
文摘By considering the joint effects of the Kelvin-Helmholtz(KH) and Rayleigh-Taylor(RT) instabilities, this paper presents an interpretation of the wavy patterns that occur in explosive welding. It is assumed that the elasticity of the material at the interface effectively determines the wavelength, because explosive welding is basically a solid-state welding process. To this end, an analytical model of elastic hydrodynamic instabilities is proposed, and the most unstable mode is selected in the solid phase. Similar approaches have been widely used to study the interfacial behavior of solid metals in high-energy-density physics. By comparing the experimental and theoretical results, it is concluded that thermal softening,which significantly reduces the shear modulus, is necessary and sufficient for successful welding. The thermal softening is verified by theoretical analysis of the increase in temperature due to the impacting and sliding of the flyer and base plates, and some experimental observations are qualitatively validated.In summary, the combined effect of the KH and RT instabilities in solids determines the wavy morphology, and our theoretical results are in good qualitative agreement with experimental and numerical observations.
文摘This study investigates the corrosion-assisted fatigue crack growth rate(FCGR)of 16 mm thick AA 7075-T651 friction stir welded(FSW)joints.Compact tension(CT)specimens were extracted from both the base material and FSW joints to evaluate FCGR under varying corrosion exposure durations(0,7,30,60,and 90 days)at a constant stress ratio of 0.5.Microstructural analysis of the welds was conducted using optical and transmission electron microscopy(TEM).Results indicate that the critical stress intensity factor range(ΔK_(cr))of FSW joints is lower than that of the base material,primarily due to precipitate dissolution in the weld zone during the FSW process,as confirmed by TEM analysis.The fatigue life of FSW joints was significantly lower than that of the base material,but with prolonged exposure to seawater corrosion,the gap in fatigue life narrowed.Specimens exposed to seawater for more than 60days exhibited minimal differences in fatigue life between the base material and the FSW joints.This was attributed to the higher corrosion rate of the base material compared to the weld nugget,resulting in the formation of deeper pits that facilitated crack initiation and accelerated fatigue failure.The findings conclude that extended corrosion exposure leads to similar fatigue life and crack growth behaviour in both the base material and FSW joints.SEM and EDX analysis of AA7075-T651 revealed corrosion pits and rust products in initiation zones,ductile striations in growth regions,and secondary cracks with micro voids in fracture zones.FSW joints exhibited ultra-fine grains,smooth ductile fracture in initiation and growth regions,and brittle fracture in the fracture zones under both corroded and uncorroded conditions.
文摘This study examines the effects of friction stir welding(FSW)and post-weld heat treatment(PWHT)on the grain boundary character distribution and corrosion resistance of cross sectional(top and bottom)regions of nickel-and molybdenum-free high-nitrogen austenitic stainless steel(HNASS).FSW at 400 rpm and 30 mm/min resulted in finer grains(4.18μm)and higher coincident site lattice(CSL)boundaries(32.3%)at the top of the stir zone(SZ)due to dynamic recrystallization(DRX).PWHT at 900℃for 1 h led to grain coarsening(12.91μm the bottom SZ)but enhanced CSL boundaries from 24.6%to 30.2%,improving grain boundary stability.PWHT reduced the kernel average misorientation(KAM)by 14.9%in the SZ-top layer and 20.4%in the SZ-bottom layer,accompanied by a 25%decrease in hardness in the SZ-top layer and 26.7%in the SZ-bottom layer,indicating strain recovery and reduced dislocation density.Potentiodynamic polarization tests(PDP)showed a 18%increase in pitting potential and a 76%reduction in corrosion rate after PWHT.The improvement in corrosion resistance is attributed to the increase inΣ3 twin boundaries,which enhance grain boundary stability and reduce susceptibility to localized corrosion.These findings highlight the role of PWHT in refining the microstructure and strengthening corrosion resistance,making HNASS a promising material for demanding applications.
基金Project (2023GK1080) supported by the Major Special Projects of Hunan Province of China。
文摘Al-Mg-Mn-Sc-Zr alloys with excellent weldability have emerged as ideal candidates for aerospace applications.Currently,the investigations on the corrosion behavior of alloys under tungsten inert gas(TIG)welding conditions are insufficient.Here,the stress corrosion cracking(SCC)behavior of base metal(BM)and weld zone(WZ)of TIG welded Al-Mg-Mn-Sc-Zr alloys was investigated by using pre-cracked compact tensile samples immersed in 3.5%NaCl solution.The direct current potential drop(DCPD)method was used to record the crack propagation.The microstructure and fracture morphology of different regions of TIG welded joints were studied by SEM,EBSD and TEM,and the SCC crack propagation mechanism of BM and WZ was analyzed.The results demonstrated that the critical stress intensity factor for stress corrosion cracking(K_(ⅠSCC))of BM and WZ was 7.05 MPa·m_(1/2) and 11.79 MPa·m_(1/2),respectively.Then,the crack propagation rate of BM was faster than that of WZ,and BM was more susceptible to SCC than WZ.Additionally,the fracture mode of the BM mainly exhibited transgranular fracture,while the fracture mode of the WZ mainly exhibited intergranular and transgranular mixed fracture.Moreover,SCC crack propagation was attributed to the combined effect of anodic dissolution and hydrogen embrittlement.This study will provide experimental and theoretical basis for the wide application of TIG welded Al-Mg-Mn-Sc-Zr alloys in aerospace.
文摘High nitrogen stainless steel(HNS) is a nickel free austenitic stainless steel that is used as a structural component in defence applications for manufacturing battle tanks as a replacement of the existing armour grade steel owing to its low cost, excellent mechanical properties and better corrosion resistance.Conventional fusion welding causes problems like nitrogen desorption, solidification cracking in weld zone, liquation cracking in heat affected zone, nitrogen induced porosity and poor mechanical properties.The above problems can be overcome by proper selection and procedure of joining process. In the present work, an attempt has been made to correlate the microstructural changes with mechanical properties of fusion and solid state welds of high nitrogen steel. Shielded metal arc welding(SMAW), gas tungsten arc welding(GTAW), electron beam welding(EBW) and friction stir welding(FSW) processes were used in the present work. Optical microscopy, scanning electron microscopy and electron backscatter diffraction were used to characterize microstructural changes. Hardness, tensile and bend tests were performed to evaluate the mechanical properties of welds. The results of the present investigation established that fully austenitic dendritic structure was found in welds of SMAW. Reverted austenite pools in the martensite matrix in weld zone and unmixed zones near the fusion boundary were observed in GTA welds. Discontinuous ferrite network in austenite matrix was observed in electron beam welds.Fine recrystallized austenite grain structure was observed in the nugget zone of friction stir welds.Improved mechanical properties are obtained in friction stir welds when compared to fusion welds. This is attributed to the refined microstructure consisting of equiaxed and homogenous austenite grains.
文摘AA5059 is one of the high strength armor grade aluminium alloy that finds its applications in the military vehicles due to the higher resistance against the armor piercing (AP) threats. This study aimed at finding the best suitable process among the fusion welding processes such as gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) by evaluating the tensile properties of AA5059 aluminium alloy joints. The fracture path was identified by mapping the low hardness distribution profile (LHDP) across the weld cross section under tensile loading. Optical and scanning electron microscopies were used to characterize the microstructural features of the welded joints at various zones. It is evident from the results that GTAW joints showed superior tensile properties compared to GMAW joints and this is primarily owing to the presence of finer grains in the weld metal zone (WMZ) and narrow heat-affected zone (HAZ). The lower heat input associated with the GTAW process effectively reduced the size of the WMZ and HAZ compared to GMAW process. Lower heat input of GTAW process results in faster cooling rate which hinders the grain growth and reduces the evaporation of magnesium in weld metal compared to GMAW joints. The fracture surface of GTAW joint consists of more dimples than GMAW joints which is an indication that the GTAW joint possess improved ductility than GMAW joint.
基金the financial support of the Directorate of Extramural Research & Intellectual Property Rights (ER&IPR)Defense Research Development Organization (DRDO)New Delhi through a R&D project no. DRDO-ERIPER/ERIP/ER/0903821/M/01/1404 to carry out this investigation
文摘Friction stir welding(FSW) is a promising welding process that can join age hardenable aluminium alloys with high joint efficiency. However,the thermal cycles experienced by the material to be joined during FSW resulted in the deterioration of mechanical properties due to the coarsening and dissolution of strengthening precipitates in the thermo-mechanical affected zone(TMAZ) and heat affected zone(HAZ). Under water friction stir welding(UWFSW) is a variant of FSW process which can maintain low heat input as well as constant heat input along the weld line. The heat conduction and dissipation during UWFSW controls the width of TMAZ and HAZ and also improves the joint properties. In this investigation, an attempt has been made to evaluate the mechanical properties and microstructural characteristics of AA2519-T87 aluminium alloy joints made by FSW and UWFSW processes. Finite element analysis has been used to estimate the temperature distribution and width of TMAZ region in both the joints and the results have been compared with experimental results and subsequently correlated with mechanical properties.? 2016 China Ordnance Society. Production and hosting by Elsevier B.V. All rights reserved.
文摘Submerged arc welding(SAW), owing to its high deposition rate and high welding quality, is widely used in the fabrication of pressure vessel, marine vessel, pipelines and offshore structures. However, selection of an optimum combination of welding parameters is critical in achieving high weld quality and productivity. In this work, initially, the SAW experiments were performed using fractional factorial design to analyze the effect of direct and indirect input parameters, namely, welding voltage, wire feed rate,welding speed, nozzle to plate distance, flux condition, and plate thickness on weld bead geometrical responses viz. bead width, reinforcement, and penetration. The bead on plate technique was used to deposit weld metal on AISI 1023 steel plates. The effect of SAW input parameters on response variables were analyzed using main and interaction effects. The linear regression was used to develop the mathematical models for the response variable. Then, the multi-objective optimization of input parameters was carried out using desirability approach, genetic algorithm and Jaya algorithm. The Jaya algorithm offered better optimization results as compared to desirability approach, genetic algorithm.
文摘The activated TIG(ATIG) welding process mainly focuses on increasing the depth of penetration and the reduction in the width of weld bead has not been paid much attention.The shape of a weld in terms of its width-to-depth ratio known as aspect ratio has a marked influence on its solidification cracking tendency.The major influencing ATIG welding parameters,such as electrode gap,travel speed,current and voltage,that aid in controlling the aspect ratio of DSS joints,must be optimized to obtain desirable aspect ratio for DSS joints.Hence in this study,the above parameters of ATIG welding for aspect ratio of ASTM/UNS S32205 DSS welds are optimized by using Taguchi orthogonal array(OA)experimental design and other statistical tools such as Analysis of Variance(ANOVA) and Pooled ANOVA techniques.The optimum process parameters are found to be 1 mm electrode gap,130 mm/min travel speed,140 A current and 12 V voltage.The aspect ratio and the ferrite content for the DSS joints fabricated using the optimized ATIG parameters are found to be well within the acceptable range and there is no macroscopically evident solidification cracking.
文摘Bead-on-plate friction stir welds were made on P91 alloy with low and high rotational speeds(100 and 1000 RPM) to study their effects on weld microstructural changes and impression creep behavior. Temperatures experienced by the stir zone were recorded at the weld tool tip. Different zones of welds were characterized for their microstructural changes, hardness and creep behavior(by impression creep tests). The results were compared with submerged arc fusion weld. Studies revealed that the stir zone temperature with 100 RPM was well below A_(c1) temperature of P91 steel while it was above A_(c3) with 1000 RPM. The results suggest that the microstructural degradation in P91 welds can be controlled by low temperature friction stir welding technique.
基金supported by National Natural Science Foundation of China(Grant No.11802141)Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX18_0465)。
文摘Three different kinds of PELE(the penetrator with lateral efficiency) were launched by ballistic artillery to impact the multi-layer spaced metal target plates.The lmpact velocities of the projectiles were measured by the velocity measuring system.The damage degree and process of each laye r of target plate impacted by the three kinds of projectiles were analyzed.The experimental results show that all the three kinds of projectiles have the effect of expanding holes on the multi-layer spaced metal target plates.For the normal structure PELE(without layered) with tungsten alloy jacket and the radial layered PELE with tungsten alloy jacket,the diameters of holes on the seco nd layer of plates are 3.36 times and 3.76 times of the diameter of the projectile,re spectively.For radial layered PELE with W/Zr-based amorphous composite jacket,due to the large number of tungsten wires dispersed after the impact,the diameter of the holes on the four-layer spaced plates can reach 2.4 times,3.04 times,5.36 times and 2.68 times of the diameter of the projectile.Besides,the normal structure PELE with tungsten alloy jacket and the radial layered PELE whit tungsten alloy jacket formed a large number of fragments impact marks on the third target plate.Although the number of fragments penetrating the third target plate is not as large as that of the normal structure PELE,the area of dispersion of fragments impact craters on the third target plate is larger by the radial layered PELE.The radial layered PELE with W/Zr-based amorphous composite jacket released a lot of heat energy due to the impact of the matrix material,and formed a large area of ablation marks on the last three target plates.
