挤压铸造ZX60镁合金组织和力学性能研究

Study on Microstructure and Mechanical Properties of Squeeze Casting ZX60 Magnesium Alloy

采用X射线衍射仪、光学显微镜、扫描电镜、透射电镜和拉伸试验研究了浇注温度和T6热处理对挤压铸造Mg-6Zn-0.1Ca-0.5Mn(ZX60)合金组织和力学性能的影响。研究表明,铸态合金的相组成为Mg基体和第二相MgZn_2相。随着浇注温度由720℃降低至680℃,铸态组织枝晶间距减小,连续、粗大的第二相趋向于弥散分布,合金屈服强度提高但抗拉强度和伸长率下降。ZX60镁合金经T6热处理后,主要强化相为沿[0001]_Mg分布的杆状MgZn_2相,其屈服强度、抗拉强度和伸长率相对于铸态分别提高了122%、62%和32%。

The influence of pouring temperature and T6 heat treatment on microstructure and mechanical properties of Mg-6Zn-0.1Ca-0.5Mn （ZX60） was investigated by means of X-Ray diffraction （XRD）, optical microscope （OM）, scanning electron microscope （SEM）, transmission electron microscope （TEM） and tensile tests. The as-cast microstructure consists of Mg matrix and second phase MgZn2. As the pouring temperature drops from 720 ℃ to 680 ℃, the dendritic spacing reduces and the continuous, coarse second phase tends to distribute more dispersedly. Besides, decreased pouring temperature is beneficial to the improvement of yielding strength but somehow lowers ultimate strength and elongation. The main strengthening phase of ZX60 alloy in T6 state is the rod-like MgZn2 precipitate lying along [0001]Mg After heat treatment, the yielding strength, ultimate strength and elongation have increased 122%, 62% and 32% in comparison with the as-cast state.