双辊薄带连铸制备Ti-43Al合金板材及其在热处理过程中的显微组织表征

摘要

To shorten the fabrication process of difficult-to-form TiAl sheets, twin-roll strip casting and microstructural control were investigated in Ti-43Al alloy. A crack-free sheet with dimensions of 1000 mm × 110 mm × 2 mm was obtained. The microstructure of stip casting sheets and heat treatments was systematically studied. The macrostructure consisted of columnar crystals extending inward and centrally located equiaxed crystals with severe Al segregation were observed along the thickness direction, due to the symmetrical solidification process and decreasing cooling rates. The strip casting alloy was characterized by fine duplex microstructure with a grain spacing of 20-30 μm and a lamellar spacing of 10-20 nm. Furthermore, multiple microstructures of near gamma, nearly lamellar and fully lamellar were obtained through heat treatment process with significantly improved homogeneity of the microstructure.%薄带连铸技术直接成形的特点可以实现难变形金属板材的制备并显著缩短流程.通过双辊薄带连铸技术制备尺寸为1000 mm×110 mm×2 mm的Ti-43Al合金板材,并对铸轧板材及热处理过程显微组织进行系统分析.由于凝固过程中冷却速率变化以及对称性生长,沿铸轧板材厚度方向出现边部柱状晶、心部等轴晶的不均匀组织,且中心区存在严重的Al元素偏析;铸轧过程中较快的冷却速度显著细化板材组织,晶粒间距为20-30μm,α2/γ片层间距达到10-20 nm.此外,铸轧板材经过热处理后获得近γ组织、近片层组织和全片层组织,组织均匀性得到明显改善.