Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing addit...Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing additive-induced defects,and alleviating residual stress and deformation,all of which are critical for enhancing the mechanical performance of the manufactured parts.Integrating interlayer friction stir processing(FSP)into WAAM significantly enhances the quality of deposited materials.However,numerical simulation research focusing on elucidating the associated thermomechanical coupling mechanisms remains insufficient.A comprehensive numerical model was developed to simulate the thermomechanical coupling behavior in friction stir-assisted WAAM.The influence of post-deposition FSP on the coupled thermomechanical response of the WAAM process was analyzed quantitatively.Moreover,the residual stress distribution and deformation behavior under both single-layer and multilayer deposition conditions were investigated.Thermal analysis of different deposition layers in WAAM and friction stir-assisted WAAM was conducted.Results show that subsequent layer deposition induces partial remelting of the previously solidified layer,whereas FSP does not cause such remelting.Furthermore,thermal stress and deformation analysis confirm that interlayer FSP effectively mitigates residual stresses and distortion in WAAM components,thereby improving their structural integrity and mechanical properties.展开更多
The dissimilar 2B06 and 7B04 Al alloy joints were prepared by refill friction stir spot welding(RFSSW),and the microstructural evolution and corrosion behavior of the joints were investigated.Based on microstructural ...The dissimilar 2B06 and 7B04 Al alloy joints were prepared by refill friction stir spot welding(RFSSW),and the microstructural evolution and corrosion behavior of the joints were investigated.Based on microstructural analysis,the welded joints exhibit distinct microstructural zones,including the stir zone(SZ),thermomechanically affected zone(TMAZ),and heat-affected zone(HAZ).The grain size of each zone is in the order of HAZ>TMAZ>SZ.Notably,the TMAZ and HAZ contain significantly larger secondary-phase particles compared to the SZ,with particle size in the HAZ increasing at higher rotational speeds.Electrochemical tests indicate that corrosion susceptibility follows the sequence of HAZ>TMAZ>SZ>BM,with greater sensitivity observed at increased rotational speeds.Post-corrosion mechanical performance degradation primarily arises from crevice corrosion at joint overlaps,but not from the changes in the microstructure.展开更多
Joining magnesium(Mg)alloys to steel is difficult due to metallurgical incompatibility.Applying a zinc(Zn)coating to steel enables formation of a thin Mg-Zn eutectic phase layer during welding,which promotes strong bo...Joining magnesium(Mg)alloys to steel is difficult due to metallurgical incompatibility.Applying a zinc(Zn)coating to steel enables formation of a thin Mg-Zn eutectic phase layer during welding,which promotes strong bonding.However,in joints created with Friction-stir assisted scribe technology(FAST),this Mg-Zn eutectic phase layer occasionally extends from the interface to the surface of the Mg sheet.This phenomenon is attributed to the formation of a liquid-state Mg-Zn eutectic phase,coupled with the distinctive material flow induced by the FAST tool.Microstructural analysis confirmed that the Mg-Zn eutectic phase comprisesα-Mg and the Mg_(21)Zn_(25)intermetallic compound.Lap shear tensile tests revealed that when the Mg-Zn eutectic phase migration pathway aligned with the stir zone boundary,it led to reduced joint strength and premature fracture along the eutectic phase pathway.This indicates that liquid metal embrittlement(LME)occurred during FAST joining of Mg alloy and galvanized steel.These findings highlight the critical importance of controlling tool features and process parameters in FAST welding to prevent LME-related failures in dissimilar Mg/steel assemblies.展开更多
This work examines the microstructure and corrosion properties of fine-grained Al 7075 across different regions under varying cooling conditions during friction stir welding.The findings demonstrate that forced coolin...This work examines the microstructure and corrosion properties of fine-grained Al 7075 across different regions under varying cooling conditions during friction stir welding.The findings demonstrate that forced cooling significantly improves the corrosion resistance of the welded joints.Specifically,the corrosion resistance was the highest in the stir zone,followed by the thermo-mechanical affected zone,and then the heat affected zone.Forced cooling mitigates grain growth by controlling the welding thermal effects,thereby increasing the proportion ofΣ3 grain boundaries.The modification of these microstructural characteristics promotes the formation of a dense oxide layer,thereby enhancing the corrosion resistance.Furthermore,forced cooling mitigates the precipitation and coarsening of the anodic phase in the stir zone,which in turn reduces the susceptibility of the joint to pitting corrosion.Additionally,the lower recrystallization texture content in the joint,resulting from forced cooling,contributes to a reduction in the number of corrosion-active sites,thereby further improving the corrosion performance of the welded joint.展开更多
搅拌摩擦搭接焊(Friction Stir Lap Welding,FSLW)作为一种固相连接技术,能有效避免材料在熔化焊接中因高温产生的气孔、热裂纹、成分偏析等问题,可实现铝/钢等异种材料的高效优质焊接。开展了AA6061-T6铝合金与QP980钢的FSLW工艺试验,...搅拌摩擦搭接焊(Friction Stir Lap Welding,FSLW)作为一种固相连接技术,能有效避免材料在熔化焊接中因高温产生的气孔、热裂纹、成分偏析等问题,可实现铝/钢等异种材料的高效优质焊接。开展了AA6061-T6铝合金与QP980钢的FSLW工艺试验,研究了不同焊接速度(恒定搅拌头转速为600r/min)对接头成形质量和焊接过程的影响。结果表明:在所研究的参数范围内,焊接速度越大,焊缝表面成形质量越高;受搅拌针搅拌作用和焊接热输入的影响,接头微观组织分为焊核区、热力影响区、热影响区和母材区,各区金相组织各异。接头力学性能测试结果发现,随着焊接速度增加,接头拉剪载荷先增后减,v=100mm/min时达到最大;显微硬度分析显示,接头铝合金侧硬度分布呈“W”形,钢侧则呈倒“V”形。此外,随着焊接速度增加导致热输入减小,焊接过程中材料塑性流动变差,焊接时搅拌头承受的载荷有所增加。展开更多
基金National Key Research and Development Program of China(2022YFB4600902)Shandong Provincial Science Foundation for Outstanding Young Scholars(ZR2024YQ020)。
文摘Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing additive-induced defects,and alleviating residual stress and deformation,all of which are critical for enhancing the mechanical performance of the manufactured parts.Integrating interlayer friction stir processing(FSP)into WAAM significantly enhances the quality of deposited materials.However,numerical simulation research focusing on elucidating the associated thermomechanical coupling mechanisms remains insufficient.A comprehensive numerical model was developed to simulate the thermomechanical coupling behavior in friction stir-assisted WAAM.The influence of post-deposition FSP on the coupled thermomechanical response of the WAAM process was analyzed quantitatively.Moreover,the residual stress distribution and deformation behavior under both single-layer and multilayer deposition conditions were investigated.Thermal analysis of different deposition layers in WAAM and friction stir-assisted WAAM was conducted.Results show that subsequent layer deposition induces partial remelting of the previously solidified layer,whereas FSP does not cause such remelting.Furthermore,thermal stress and deformation analysis confirm that interlayer FSP effectively mitigates residual stresses and distortion in WAAM components,thereby improving their structural integrity and mechanical properties.
基金supported by the National Natural Science Foundation of China (Nos. 52075449, 51975480)。
文摘The dissimilar 2B06 and 7B04 Al alloy joints were prepared by refill friction stir spot welding(RFSSW),and the microstructural evolution and corrosion behavior of the joints were investigated.Based on microstructural analysis,the welded joints exhibit distinct microstructural zones,including the stir zone(SZ),thermomechanically affected zone(TMAZ),and heat-affected zone(HAZ).The grain size of each zone is in the order of HAZ>TMAZ>SZ.Notably,the TMAZ and HAZ contain significantly larger secondary-phase particles compared to the SZ,with particle size in the HAZ increasing at higher rotational speeds.Electrochemical tests indicate that corrosion susceptibility follows the sequence of HAZ>TMAZ>SZ>BM,with greater sensitivity observed at increased rotational speeds.Post-corrosion mechanical performance degradation primarily arises from crevice corrosion at joint overlaps,but not from the changes in the microstructure.
基金PNNL is operated by Battelle Memorial Institute for the U.S.Department of Energy under contract DE-AC05-76RL01830sponsored by the DOEEERE,Vehicle Technology Office,through the Joining Core Program.
文摘Joining magnesium(Mg)alloys to steel is difficult due to metallurgical incompatibility.Applying a zinc(Zn)coating to steel enables formation of a thin Mg-Zn eutectic phase layer during welding,which promotes strong bonding.However,in joints created with Friction-stir assisted scribe technology(FAST),this Mg-Zn eutectic phase layer occasionally extends from the interface to the surface of the Mg sheet.This phenomenon is attributed to the formation of a liquid-state Mg-Zn eutectic phase,coupled with the distinctive material flow induced by the FAST tool.Microstructural analysis confirmed that the Mg-Zn eutectic phase comprisesα-Mg and the Mg_(21)Zn_(25)intermetallic compound.Lap shear tensile tests revealed that when the Mg-Zn eutectic phase migration pathway aligned with the stir zone boundary,it led to reduced joint strength and premature fracture along the eutectic phase pathway.This indicates that liquid metal embrittlement(LME)occurred during FAST joining of Mg alloy and galvanized steel.These findings highlight the critical importance of controlling tool features and process parameters in FAST welding to prevent LME-related failures in dissimilar Mg/steel assemblies.
基金Project(ASM-20240)supported by the Key Laboratory of Advanced Structural Materials(Changchun University of Technology),Ministry of Education,ChinaProject(2022TD-30)supported by the Scientific and Technological Innovation Team Project of Shaanxi Innovation Capability Support Plan,China。
文摘This work examines the microstructure and corrosion properties of fine-grained Al 7075 across different regions under varying cooling conditions during friction stir welding.The findings demonstrate that forced cooling significantly improves the corrosion resistance of the welded joints.Specifically,the corrosion resistance was the highest in the stir zone,followed by the thermo-mechanical affected zone,and then the heat affected zone.Forced cooling mitigates grain growth by controlling the welding thermal effects,thereby increasing the proportion ofΣ3 grain boundaries.The modification of these microstructural characteristics promotes the formation of a dense oxide layer,thereby enhancing the corrosion resistance.Furthermore,forced cooling mitigates the precipitation and coarsening of the anodic phase in the stir zone,which in turn reduces the susceptibility of the joint to pitting corrosion.Additionally,the lower recrystallization texture content in the joint,resulting from forced cooling,contributes to a reduction in the number of corrosion-active sites,thereby further improving the corrosion performance of the welded joint.
文摘搅拌摩擦搭接焊(Friction Stir Lap Welding,FSLW)作为一种固相连接技术,能有效避免材料在熔化焊接中因高温产生的气孔、热裂纹、成分偏析等问题,可实现铝/钢等异种材料的高效优质焊接。开展了AA6061-T6铝合金与QP980钢的FSLW工艺试验,研究了不同焊接速度(恒定搅拌头转速为600r/min)对接头成形质量和焊接过程的影响。结果表明:在所研究的参数范围内,焊接速度越大,焊缝表面成形质量越高;受搅拌针搅拌作用和焊接热输入的影响,接头微观组织分为焊核区、热力影响区、热影响区和母材区,各区金相组织各异。接头力学性能测试结果发现,随着焊接速度增加,接头拉剪载荷先增后减,v=100mm/min时达到最大;显微硬度分析显示,接头铝合金侧硬度分布呈“W”形,钢侧则呈倒“V”形。此外,随着焊接速度增加导致热输入减小,焊接过程中材料塑性流动变差,焊接时搅拌头承受的载荷有所增加。
