高Ca含量Mg-13Zn-0.5Nd合金组织与力学性能

Effect of High Ca Content on Microstructure and Mechanical Property of Mg-13Zn-0.5Nd Alloy

以气体保护法制备的Mg-13Zn-0.5Nd-xCa(x=3,4,5,6)合金为研究对象,通过光学金相显微镜、扫描电镜观察、能谱分析、XRD物相分析以及硬度和常温力学性能测试,研究了因含Ca量的不同对该类型合金显微组织和力学性能的影响。合金铸态组织主要由α-Mg基体相、α-Mg+Mg_6Zn_3Ca_2共晶相以及第二相Mg_2Ca和Mg_6Zn_3Ca_2组成,随着含Ca量的增加,晶粒明显细化。经390℃,8 h固溶处理和240℃,8 h人工时效处理后,消除了共晶组织连续网状分布状态,使更多的第二相析出且弥散分布,提高了合金的常温力学性能。Ca加入量为4%时,合金在T6处理后表现出最好的综合力学性能,峰时效态合金的屈服强度和抗拉强度达到108和175 MPa,伸长率为6.10%,该合金优异的力学性能主要是第二相强化和细晶强化的双重效果。

The Mg-13Zn-0.5Nd-xCa （x=3, 4, 5, 6） alloys containing high-calcium have been prepared under the protection of a mix gas atmosphere of Ar. The alloy composites were characterized by X-ray diffraction, optical metallurgical microscope, scanning electron microscope and mechanical property test. The effect of high Ca content on microstructure and mechanical properties of the alloy was investigated. The results show that the alloy is mainly composed of a-Mg matrix, a-Mg＋Mg6ZnaCa2 eutectic phase and a few secondary phase （Mg2Ca＋Mg6Zn3Ca2） in as-cast state. The grain is extremely refined with the increase of Ca addition. After the solution treatment at 390 ~C for 8 h and subsequent aging at 240 ~C for 8 h, the alloy exhibits excellent mechanical properties. The optimum mechanical property of the alloy is obt3ined by 4% Ca addition after T6 heat treatment. The ultimate tensile strength, yield strength and elongation of the alloy at peak-aged state are 108 MPa, 175 MPa and 6.10% at room temperature, respectively. The good mechanical properties are mainly attributed to fine grain strengthening and second phase strengthening