(武漢理工大學(xué) 材料科學(xué)與工程學(xué)院，武漢 430070)
摘 要: 采用SEM、EDS和XRD等測試手段，研究Mg-50%TiB2(質(zhì)量分數(shù))中間合金和堿土金屬元素Ca對AZ91D鎂合金組織和性能的影響。結(jié)果表明：0.7%TiB2和0.1%Ca可以顯著細化AZ91D鎂合金的枝晶組織和晶粒，α-Mg的平均晶粒尺寸由240 μm下降至46 μm。通過能譜分析及面錯配度的計算證實：TiB2顆粒可作為初生α-Mg的良好異質(zhì)形核核心。堿土金屬元素Ca在晶界處富集，阻礙了α-Mg晶粒生長，對晶粒細化起到了一定的作用。顯微組織的細化使合金的強韌性明顯提高，并對耐腐蝕性能有較大改善。
關(guān)鍵字: AZ91D鎂合金；Mg-TiB2中間合金；Ca；晶粒細化
properties of AZ91D magnesium alloy
（School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China）
Abstract: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 boundaries 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.
Key words: AZ91D magnesium alloy; Mg-TiB2 master alloy; Ca; grain refinement
