Formation of Al2Ca Phase in as-Extruded X20 Magnesium Alloy by Solution Treatment

摘要:

对Ca含量为2wt%的挤压态X20镁合金在410 ℃固溶处理20 h，采用光学显微镜 (OM)、扫描电镜 (SEM) 结合能谱分析 (EDS)以及透射电镜 (TEM) 对固溶处理前后的组织进行了表征，利用XRD衍射仪考察了固溶处理前后合金的相组成。结果表明，经固溶处理后，合金初始组织中β-Mg17Al12相的数量明显减少，同时析出新相Al2Ca。Al2Ca的形成可归结于残余β-Mg17Al12中高的Ca原子所造成的Mg原子被Ca原子取代，同时Al2Ca相自身高的结构稳定性也是其在Mg-Ca和Al-Ca系竞争析出中胜出的原因

Abstract:

The as-extruded X20 magnesium alloys containing 2.0wt% Ca were solution-treated at 410 oC for 20 h. The microstructures before and after solution treatment were observed by optical microscope (OM), scanning electron microscope (SEM) together with an energy dispersive spectroscope (EDS), and transmission electron microscope (TEM). The phase compositions before and after solution treatment were confirmed by X-ray diffraction (XRD). The results show that the amount of β-Mg17Al12 phases decreases remarkably after solution treatment, and new Al2Ca phases are formed. The formation of Al2Ca phase might be due to high concentration of Ca atoms in residual β-Mg17Al12 phases, which leads the place of Mg atoms to be substituted by Ca. On the other hand, Al2Ca phase could be also described as a completing product between Al-Ca system and Mg-Ca system intermetallics due to its high structural stability