AE42合金的抗压入蠕变性能

Indentation creep resistance of AE42 alloy

采用自制实验装置对Mg-Al-2RE(AE42)合金进行压入蠕变实验,利用带能谱(EDS)的扫描电镜(SEM)和X射线衍射(XRD)分析合金蠕变前后的组织和成分的演化。结果表明:随温度或应力的增加,AE42合金的压入蠕变速率和第一阶段的蠕变量逐渐增加;合金在压入状态下的蠕变应力指数和蠕变激活能的均值分别为3.06和72.4kJ/mol;压入条件下AE42合金的稳态蠕变速率由晶界扩散主导的位错粘滞性滑移控制;铸态AE42合金由α-Mg基体、针状Al11La3和少量颗粒状Al2La组成;固溶处理8h后,合金中的β-Mg17Al12相溶入α-Mg基体,合金的硬度上升;固溶24h后,晶粒得到粗化,合金的硬度和抗蠕变性能均下降;固溶处理后再人工时效24h,晶粒略有细化,但大量β-Mg17Al12相沿晶界不连续析出,合金的硬度和抗蠕变性能进一步下降。

The indentation creep property of Mg-4Al-2RE （AE42） alloy was analyzed with a special apparatus. The microstructure and compositions of precipitated phases were performed by scanning electron microscope （SEM） with energy dispersive spectrometer （EDS） and X-ray diffractometry （XRD）. The results reveal that the steady creep rates and primary indentation deformation of AE42 alloy increase with increasing temperature and stress. The average stress exponent and creep activity energy are 3.06 and 72.4 kJ/mol, respectively. The indentation steady creep rate is controlled by dislocation viscosity slipping led by the grain boundary diffusion. The as-cast AE42 alloy consists of a-Mg matrix, acicular Al11La3 and granular AlzLa. The microhardness of AE42 alloy is increased after solution for 8 h as the result of fl-Mg17Al12 phase dissolving into a-Mg matrix. But the microhardness and creep resistance of AE42 alloy decrease after solution for 24 h because of the grains coarsening. The microhardness and creep resistance decrease further after 24 h ageing treatment for large number of fl-MglTAl12 phase precipitated discontinuously at the grain boundaries notwithstanding the grains are fined a little.