共晶Si形貌与A356铝合金的动态、准静态压缩变形下的力学性能及抗氢脆性能的影响密切相关。因此文章通过Material Test System(MTS)及霍普金森压杆(SHPB)测试变质前后A356铝合金的动态/准静态压缩力学行为,并采用电化学充氢方法研究合...共晶Si形貌与A356铝合金的动态、准静态压缩变形下的力学性能及抗氢脆性能的影响密切相关。因此文章通过Material Test System(MTS)及霍普金森压杆(SHPB)测试变质前后A356铝合金的动态/准静态压缩力学行为,并采用电化学充氢方法研究合金的抗氢脆性能。结果表明,准静态压缩变形后,合金中板状共晶Si垂直于压缩方向破裂成颗粒状。细化后的共晶Si提高了合金的塑性,延缓了合金的失效。而动态压缩变形后,板状共晶Si变形不均匀,并且碎成块状的共晶Si的尖端在压缩过程中会切割基体,导致其附近出现裂纹等缺陷。随着应变速率增大,铸态A356合金的屈服强度及抗压强度逐渐增大,合金具有一定的应变速率敏感性。变质后,共晶Si得到细化,增大了Al/Si接触面积,共晶Si捕获原子氢后降低了其与基体的连结,导致合金在拉伸变形过程中裂纹更易沿其扩展,并且细化后的共晶Si会进一步降低合金的抗氢脆性能力。其中细化后残存的块状共晶Si在捕获原子氢后会出现脱粘现象,易成为裂纹萌发点。展开更多
Nowadays,having an effective technique in preparing semi-solid slurries for rheocasting process seems to be an essential requirement.In this study,semi-solid slurry of A356 aluminum alloy was prepared by three-phase a...Nowadays,having an effective technique in preparing semi-solid slurries for rheocasting process seems to be an essential requirement.In this study,semi-solid slurry of A356 aluminum alloy was prepared by three-phase annular electromagnetic stirring(A-EMS)technique under different conditions.The effects of stirring current,pouring temperature and stirring time on microstructural evolution,mean particle size,shape factor and solid fraction were investigated.The rheocasting process was carried out by using a drop weight setup and to inject the prepared semi-solid slurry in optimal conditions into the step-die cavity.The filling behavior and mechanical properties of parts were studied.Microstructural evolution showed that the best semi-solid slurry which had fine spherical particles with the average size of~27μm and a shape factor of~0.8 was achieved at the stirring current of 70 A,melt pouring temperature of 670℃,and stirring time of 30 s.Under these conditions,the step-die cavity was completely filled at die preheating temperature of 470℃.The hardness increases by decreasing step thickness as well as die preheating temperature.Moreover,the tensile properties are improved at lower die preheating temperatures.The fracture surface,which consists of a complex topography,indicates a typical ductile fracture.展开更多
文摘共晶Si形貌与A356铝合金的动态、准静态压缩变形下的力学性能及抗氢脆性能的影响密切相关。因此文章通过Material Test System(MTS)及霍普金森压杆(SHPB)测试变质前后A356铝合金的动态/准静态压缩力学行为,并采用电化学充氢方法研究合金的抗氢脆性能。结果表明,准静态压缩变形后,合金中板状共晶Si垂直于压缩方向破裂成颗粒状。细化后的共晶Si提高了合金的塑性,延缓了合金的失效。而动态压缩变形后,板状共晶Si变形不均匀,并且碎成块状的共晶Si的尖端在压缩过程中会切割基体,导致其附近出现裂纹等缺陷。随着应变速率增大,铸态A356合金的屈服强度及抗压强度逐渐增大,合金具有一定的应变速率敏感性。变质后,共晶Si得到细化,增大了Al/Si接触面积,共晶Si捕获原子氢后降低了其与基体的连结,导致合金在拉伸变形过程中裂纹更易沿其扩展,并且细化后的共晶Si会进一步降低合金的抗氢脆性能力。其中细化后残存的块状共晶Si在捕获原子氢后会出现脱粘现象,易成为裂纹萌发点。
基金Central Applied Research Laboratory(CARL)Center of Materials ResearchDepartment of Materials Science and Metallurgy,Shahid Bahonar University of Kerman(SBUK)for support of this work。
文摘Nowadays,having an effective technique in preparing semi-solid slurries for rheocasting process seems to be an essential requirement.In this study,semi-solid slurry of A356 aluminum alloy was prepared by three-phase annular electromagnetic stirring(A-EMS)technique under different conditions.The effects of stirring current,pouring temperature and stirring time on microstructural evolution,mean particle size,shape factor and solid fraction were investigated.The rheocasting process was carried out by using a drop weight setup and to inject the prepared semi-solid slurry in optimal conditions into the step-die cavity.The filling behavior and mechanical properties of parts were studied.Microstructural evolution showed that the best semi-solid slurry which had fine spherical particles with the average size of~27μm and a shape factor of~0.8 was achieved at the stirring current of 70 A,melt pouring temperature of 670℃,and stirring time of 30 s.Under these conditions,the step-die cavity was completely filled at die preheating temperature of 470℃.The hardness increases by decreasing step thickness as well as die preheating temperature.Moreover,the tensile properties are improved at lower die preheating temperatures.The fracture surface,which consists of a complex topography,indicates a typical ductile fracture.
