Mg-Gd-Y-Zr合金的高温时效行为研究

通过金相显微镜、扫描电镜、X射线衍射等手段分析了金属型及砂型铸造Mg-Gd-Y-Zr合金高温下的时效析出行为.结果表明,经高温时效处理后,合金主要由Gd+Y在Mg中的过饱和固溶体、方块相、少量球状的Zr核及β相组成;高温时效处理几乎不影响合金的晶粒尺寸,随着时效温度的提高及高温时效时间的延长,合金的硬度逐渐降低;在晶内析出了呈三角取向或单一平行取向分布的β相,晶界上出现无沉淀析出带;成形条件并不影响高温时效析出相的分布和趋向.

Elevated Aging Behavior of Mg-Gd-Y-Zr Alloy

Elevated aging precipitation behaviors of permanent mould and sand mold casting Mg-Gd-Y-Zr alloys were observed by OM (optical microscope), SEM (scanning electron microscope) and XRD (X-ray diffraction). The results show that the T4 alloy aged at elevated temperatures is composed of α-Mg solid solution with (Gd+Y) phase and cuboidal particle and a little spheroidized Zr nuclei as well as β phase. Average grain size in the T4 alloy is nearly independent of the elevated aging treatment processes, however, with increasing in aging temperature and in aging time, hardness of the alloy is slowly decreased. In addition, the β phase distributed in trigonal and parallel orientation in the grain can be observed, and precipitates-free zone (PFZ) appears in the grain boundary. Distribution and orientation of precipitates in the alloy at elevated aging is independent of the forming conditions.