均匀化处理及冷却方式对Mg-Y-Zn合金显微组织及硬度的影响

利用X射线衍射、光学显微镜、扫描电镜和硬度测试等方法研究了均匀化处理以及冷却方式对Mg-Y-Zn合金显微组织及硬度的影响。结果表明:铸态合金的组织由α-Mg基体、连续网状分布的层片状LPSO相及不规则块状Mg24Y5共晶相构成。均匀化处理过程中,Mg24Y5共晶相逐渐溶解,层片状LPSO相沿平行片层方向向晶粒内部持续生长直至贯穿整个晶粒,并在垂直片层方向发生聚集粗化。相较于水冷态合金,炉冷态合金晶粒内部析出细小弥散的针状相。硬度测试结果表明:均匀化处理初期,合金硬度得到一定程度的提升;进一步延长均匀化处理时间,合金硬度降低。其次,炉冷态合金硬度低于水冷态合金。

Effects of homogenization and cooling method on microstructure and hardness of Mg-Y-Zn alloy

Effects of homogenization and cooling method on microstructure and hardness of Mg-Y-Zn alloy were studied by means of X-ray diffraction, optical microscope(OM), scanning electron microscopy and hardness test. The results show that the microstructure of the as-cast alloy is composed of α-Mg matrix, lamellar LPSO phase with continuous net-like distribution and irregular bulk Mg24Y5 eutectic phase. In the process of homogenization, the eutectic phase of Mg24Y5 dissolves gradually, and the lamellar LPSO phase grows continuously along the direction of parallel lamellar until it penetrates the whole grain, and aggregates and coarsens in the direction of vertical lamellar. Compared with water-cooled alloy, the fine dispersed needle-like phase is precipitated in the grain of furnace-cooled alloy. The hardness test results show that the hardness of the alloy is slightly increased at the beginning of homogenization treatment, and the hardness of the alloy decreases when the homogenization treatment time is further prolonged. Besides, the hardness of the furnace cooled alloy is lower than that of the water cooled alloy.