Sn对铸态Mg-6Zn-0.7Zr合金组织及力学性能的影响

Effects of Sn Content on Microstructure and Mechanical Properties of As-cast Mg-6Zn-0.7Zr Alloy

通过XRD、SEM、EDS分析以及拉伸试验等手段,研究了铸态Mg-6Zn-0.7Zr-xSn(x=0,0.5,1,2,3)合金的显微组织和力学性能。结果表明,Mg-6Zn-0.7Zr合金中的Sn主要有3种存在形式:固溶于α-Mg基体、形成Mg2Sn相、少量固溶于MgZn相;Sn的添加可细化MgZn离异共晶相,但粗化了α-Mg枝晶,表明含Sn镁合金中不适合添加Zr元素;少量Sn的添加可以改善Mg-6Zn-0.7Zr合金的强度。当Sn含量为0.5%时,合金铸态的抗拉强度和伸长率分别为242MPa和17%;当Sn含量达到3%以后,合金拉伸断口形貌中存在大量的解理台阶面和河流状花样,合金脆性增大。

Effect of different Sn additions on microstructure and mechanical properties of as-cast Mg-6Zn-0.7Zr alloys were investigated by XRD (X-ray diffraction), SEM (scanning electron microscope), EDS (energy dispersive spectrum) and tensile testing. The results show that Sn exists in the Mg-6Zn-0.7Zr alloy in form of three types: dissolved in α-Mg matrix, formed Mg2Sn phases, and existed in the MgZn phase. The addition of Sn can refine the divorced MgZn eutectics. However, the increase of Sn leads to the coarseness of α-Mg dendritic, which indicates that magnesium alloys containing Sn are not suitable for the addition of Zr element. A minor addition of Sn can improve the tensile strength of as-cast Mg-6Zn-0.7Zr alloy. The tensile strength and elongation of Mg-6Zn-0.7Zr-0.5Sn alloy reach 242 MPa and 17%, respectively. Fractographic analysis demonstrates that the brittleness of the alloy increases when the Sn content is over 3%. It is expressed as a large number of dissociation stepped surface and river pattern on the fracture surface.