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 microstructure and mechanical properties of pure magnesium

摘要:

本文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。研究结果表明：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-6.4wt.%Zn合金和Mg-8（Mg+8wt.%Zn-Mg-Ti中间合金）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308MPa和21.5%。

关键词:Zn-Mg-Ti中间合金;镁合金;第二相;微观组织;力学性能

Abstract:

In this paper, a Zn-Mg-Ti master alloy was prepared by mould casting, and the effect of Zn-Mg-Ti master alloy on the microstructure and mechanical properties of pure magnesium were studied. The results showed that the master alloy was mainly composed of matrix and flower-like Zn-Mg-Ti ternary phase, and that the Zn-Mg-Ti master alloy had a significant influence on the microstructure and mechanical properties of pure magnesium. The grain size of magnesium alloy decreased first and then increased with the increase of master alloy addition; when the addition amount of the master alloy was 8%, the finest grain size could 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 grow. Compared with the microstructure of the Mg-6.4wt.% Zn alloy and M-8 alloy, it was found that Ti element could 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 of as-extruded alloys showed that the strength and elongation of magnesium alloy increased first and then decreased with the increase of addition amount of the master alloy; when the content of the master alloy was 8%, the ultimate tensile strength and elongation of the magnesium alloy were 308 MPa and 21.5%, respectively.

Key words:Zn-Mg-Ti master alloy; magnesium alloy; second phase; microstructure; mechanical properties