Zn-Mg-Ti中间合金对纯镁组织及性能的影响

Effect of Zn-Mg-Ti Master Alloy on the Microstructure and Mechanical Properties of Pure Magnesium

通过模铸法制备了一种Zn-Mg-Ti中间合金,并研究分析了Zn-Mg-Ti中间合金对纯镁显微组织和力学性能的影响。结果表明:中间合金主要由基体及"花朵状"Zn-Mg-Ti三元相组成。Zn-Mg-Ti中间合金对纯镁的晶粒组织有显著影响,镁合金晶粒尺寸随中间合金添加量的增大先减小后增大,当中间合金添加量为8%时,镁合金晶粒尺寸最小。镁合金晶粒细化主要归因于Ti原子在固液界面前沿偏聚,造成成分过冷,抑制晶粒长大。对比Mg-6.4%Zn合金和M-8(Mg+8%Zn-Mg-Ti中间合金)(质量分数)合金微观组织,发现Ti元素不仅能显著细化Mg-Zn合金晶粒尺寸,而且能够促进M-8合金中的第二相固溶于基体中。挤压态合金力学性能测试结果表明,镁合金力学性能随Zn-Mg-Ti中间合金添加量增加先增大后减小,当中间合金添加量为8%时,镁合金综合力学性能最佳,其抗拉强度和延伸率分别为308 MPa和21.5%。

A Zn-Mg-Ti master alloy was prepared by mould casting,and the effects of Zn-Mg-Ti master alloy on the microstructure and mechanical properties of pure magnesium were studied.The results show that the master alloy is mainly composed of matrix and flower-like Zn-Mg-Ti ternary phase,and that the Zn-Mg-Ti master alloy has a significant influence on the microstructure and mechanical properties of pure magnesium.The grain size of the magnesium alloy decreases first and then increases with the increase of the master alloy addition in amount;when the addition amount of the master alloy is 8%,the finest grain size can be obtained.The grain refinement of the magnesium alloy is mainly attributed to the Ti atoms that agglomerate at the front of the solid-liquid interface and thus restrict the crystal to growth.Comparing the microstructures of the Mg-6.4 wt% Zn alloy and M-8(Mg+8 wt%Zn-Mg-Ti) alloy,it is found that Ti element can not only significantly refine grain size of Mg-Zn alloy,but also promote the dissolution of the second phase into the matrix.The mechanical properties test of as-extruded alloys show that the strength and elongation of magnesium alloy increase first and then decrease with the increase in amount of the master alloy addition;when the content of the master alloy is 8%,the ultimate tensile strength and elongation of the magnesium alloy are 308 MPa and 21.5%,respectively.