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采用恒速及跃迁减速定向凝固方法制备了Al-40%Cu(质量分数)过共晶合金,对金属间化合物初生Al2Cu相的组织及取向演化进行了研究.结果表明,当定向凝固速率恒定为10μm/s,抽拉100 mm时,合金成分随着凝固距离的增大而减小,初生Al2Cu相枝晶由规则棱面V型转变为非棱面形貌,在抽拉距离80 mm附近消失,其生长方向由[110]方向转变为(121)晶面的法线方向;当定向凝固速率由10μm/s跃迁减速至2μm/s时,合金成分在变速界面后随着凝固距离的增大先增大后减少,初生Al2Cu相枝晶由规则棱面V型变为非棱面长条状形貌而后消失,其体积分数先增大后减少,Al2Cu相的生长方向由[110]方向转变为平行于热流方向的[001]方向.定向凝固恒速与跃迁变速下初生Al2Cu相枝晶生长机制存在异同,凝固工艺参数成为影响枝晶最终组织形态和生长方向的主要因素.
Al-40% Cu (mass fraction) hypereutectic alloy was prepared by constant-rate and transition-slowed directional solidification method to study the microstructure and orientation evolution of Al2Cu primary phase intermetallic compounds.The results show that when the directional solidification rate is constant 10μm / s. When the drawing distance is 100mm, the alloy composition decreases with the increase of the solidification distance. The primary Al2Cu phase dendrite changes from a regular faceted V-shape to a non-faceted shape and disappears near the drawing distance of 80mm , The growth direction changes from the [110] direction to the normal direction of the (121) crystal plane. When the directional solidification rate decelerates from 10μm / s to 2μm / s, the alloy composition increases with the solidification distance First increase and then decrease, primary Al2Cu phase dendrite from the regular facets V-shaped non-faceted long strip morphology and then disappear, the volume fraction first increased and then decreased, Al2Cu phase growth direction by the [110] direction change Which is parallel to the direction of [001] in the direction of heat flux.It is found that there are similarities and differences in the growth mechanism of primary Al2Cu phase dendrites at constant speed of directional solidification and transitional speed change, and the solidification process parameters are the main factors that affect the final morphology and growth direction of dendrite.