含钪、铒的Al-0.8%Mg-0.6%Si合金的低周疲劳行为

Low-Cycle Fatigue Behavior of Al-0.8%Mg-0.6%Si Alloys Containing Scandium and Erbium

对固溶+人工时效(T6)处理的挤压变形Al-0.8%Mg-0.6%Si,Al-0.8%Mg-0.6%Si-0.2%Sc和Al-0.8%Mg-0.6%Si-0.3%Er合金进行了低周疲劳试验,探讨了合金的低周疲劳变形和断裂行为。结果表明,低周疲劳变形期间,含Sc,Er合金可以呈现循环应变硬化、循环应变软化和循环稳定;添加稀土元素Sc可提高合金的循环变形抗力,且含0.2%Sc的合金在疲劳变形期间发生双系滑移;含Sc,Er合金的弹性应变幅和塑性应变幅与断裂时的载荷反向周次的关系可分别用Basquin和Coffin-Manson公式来描述,其中Al-0.8%Mg-0.6%Si-0.2%Sc合金的塑性应变幅与断裂时的载荷反向周次之间呈双线性关系;含Sc,Er合金的疲劳裂纹均是以穿晶方式萌生于试样表面,并以穿晶方式扩展。

The low-cycle fatigue tests were conducted for extruded Al-0.8%Mg-0.6%Si,Al-0.8%Mg-0.6%Si-0.2%Sc and Al-0.8%Mg-0.6%Si-0.3%Er alloys subjected to solution plus artificial aging treatment.The fatigue deformation and fracture behavior of the alloys were investigated.The results showed that during the cyclic deformation,the alloys containing Sc and Er exhibited the cyclic strain hardening,cyclic strain softening and cyclic stability.The addition of Sc could improved the cyclic deformation resistance of the alloy.The double-system slip occured for the alloy containing 0.2%Sc during the fatigue deformation.For the alloys containing Sc and Er,the relationship between elastic strain amplitude and plastic strain amplitude with reversals to failure could be described by Basquin and Coffin-Manson equations respectively.And the bilinear relation between plastic strain amplitude and reversals to failure could be noted for the Al-0.8%Mg-0.6%Si-0.2%Sc alloy.The fatigue crack initiated transgranularly on the surface of fatigue samples and propagated in a transgranular mode for the alloys containing Sc and Er.