Zn元素对Mg-6Al-2Nd-2Ca组织和性能的影响

Effects of Zn on Microstructure and Mechanical Property of Mg-6Al-2Nd-2Ca Alloy

摘要:

采用金属型重力铸造方法制备了Mg-6Al-2Nd-2Ca和Mg-6Al-2Nd-2Ca-1.2Zn合金，并对铸态合金进行均匀化处理和热挤压加工，通过金相显微镜、X射线衍射仪、扫描电镜、能谱仪、透射电镜和万能拉伸实验机等分析测试方法，研究了Zn元素对Mg-6Al-2Nd-2Ca合金显微组织和力学性能的变化。实验结果表明：Zn元素的加入有助于细化晶粒，Zn在合金中主要以固溶体的形式存在，降低了Al在α-Mg基体中的固溶度，生成更多的Al-Nd相。两种合金经过均匀化处理后，与铸态相比显微组织更加均匀，第二相数量略有减少。经热挤压后，两种合金中的硬脆相被挤碎，晶粒得到明显的细化，力学性能明显提升，在细晶强化、第二相强化的共同作用下Mg-6Al-2Nd-2Ca-1.2Zn合金表现出优良的力学性能，其抗拉强度、屈服强度和断后伸长率分别为294.0 MPa、197.1 MPa、11.6%。

Abstract:

Mg-6Al-2Nd-2Ca alloy and Mg-6Al-2Nd-2Ca-1.2Zn alloy were prepared by the gravity casting method in a permanent mould. The as-cast alloys were homogenized, hot extruded and thereafter tested and analyzed by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and tensile test. Effect of Zn addition on the microstructure and mechanical properties of Mg-6Al-2Nd-2Ca alloy were analyzed. The experimental results show that the addition of Zn could refine grains, which mainly exist in the α-Mg matrix, reduce the solid solubility of Al in the α-Mg matrix and generate more Al-Nd phases. After homogenization treatment, the microstructure of the two alloys were more uniform, and the amount of precipitated phase was reduced compared with that of the as-cast alloys. After hot extrusion, the hard and brittle phases in the two alloys were crushed, the grains was refined, and the mechanical properties was obviously improved. The tensile strength, yield strength and elongation of the Mg-6Al-2Nd-2Ca-1.2Zn were 294.0 MPa, 197.1 MPa and 11.6%, respectively, which were attributed to the combination of refinement strengthening and second phase strengthening.