Mg-TiB2中间合金和Ca对AZ91D镁合金组织和性能的影响

摘要

The microstructures and properties of AZ91D magnesium alloy with Mg-50％TiB2 (mass faction) and Ca were studied using SEM, EDS and XRD. It is found that combining addition of 0.7％TiB2 and 0.1％Ca to AZ91D magnesium alloy leads to the α-Mg grain size decreasing from 240 to 46 μm. Based on the EDS test results and calculation of the planar disregistry between TiB2 and α-Mg, TiB2 particles can act as the heterogeneous nucleus of primary α-Mg phase. Ca is pushed onto the solid/liquid interface and enriched at grain boundarries during solidification, which leads to the grain refinement due to the restriction of grain growth. The microstructural refinement of AZ91D magnesium alloy produces significant improvement of mechanical properties and corrosion resistance.%采用SEM、EDS和XRD等测试手段,研究Mg-50%TiB2(质量分数)中间合金和碱土金属元素Ca对AZ91D镁合金组织和性能的影响.结果表明:0.7%TiB2和0.1%Ca可以显著细化AZ91D镁合金的枝晶组织和晶粒,α-Mg的平均晶粒尺寸由240 μm下降至46 μm.通过能谱分析及面错配度的计算证实:TiB2颗粒可作为初生α-Mg的良好异质形核核心.碱土金属元素Ca在晶界处富集,阻碍了α-Mg晶粒生长,对晶粒细化起到了一定的作用.显微组织的细化使合金的强韧性明显提高,并对耐腐蚀性能有较大改善.