定向凝固过共晶合金Al-Al_2Cu的组织演化及取向分析  

MICROSTRUCTURE EVOLUTION AND ORIENTATION ANALYSIS OF HYPEREUTECTIC Al-Al_2Cu ALLOY UNDER DIRECTIONAL SOLIDIFICATION

作　　者：高卡 李双明[1] 傅恒志[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室,西安710072

出　　处：《金属学报》2014年第8期962-970,共9页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目50971101和51074127;凝固技术国家重点实验室自主研究课题项目34-TP-2009资助;Supported by National Natural Science Foundation of China(Nos.50971101 and 51074127);Fund of State Key Laboratory of Solidification Processing in NWPU(No.34-TP-2009)

摘　　要：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.Dendrite is a fundamental growth pattern in alloy solidification. Normally, dendrites with a specif- ic growth orientation which can remarkably influence casting properties have attracted many great interests. The previous investigations mainly focus on the growth of simple monophase dendrites solid solution. For complex in- termetallics in solidification, the correlation between processing parameters and microstructure morphologies with the preferred growth directions has not been shed a light. In this work, considering intermetallic AI2Cuphase has crystalline anisotropy and can exhibit colorfully complicated growth morphologies with specific growth direction in different solidification conditions, the primaryAI2Cu phase growth behavior of A1-40%Cu （mass fraction） hyper- eutectic alloy was investigated by using a high thermal gradient directional solidification apparatus. The AI2Cuphase growth behavior in the experiments included its change in growth morphology and orientation transition. With solidification distance increasing, due to the alloy liquid composition ahead of the solid/liquid interface ap- proaching the eutectic point, the primaryAI2Cu dendrite transited from regular faceted V-shaped morphology to theentirely coupled eutectic at 10 μm/s. Its growth direction changed from [110] direction to the normal direction of （121） plane. The EBSD result indicated that the [001 ] direction of A12Cu phase was along the direction of heat flux. As the growth rate was changed abruptly from 10 to 2 μm/s, the alloy liquid composition ahead of the solid/liquid interface increased firstly and then decreased to the eutectic point. It caused that the primary AI2Cu dendrite transit- ed from regular faceted V-shaped morphology to long smooth lath morphology, and finally disappeared to form the entirely coupled eutectic. Moreover, the growth direction of ALCu phase changed from [110] direction to [001 ] di- rection. The experimental results show that the directional solidification process parameter is the dominant

关 键 词：定向凝固 速率跃迁 金属间化合物Al2Cu相 取向 

分 类 号：TG292[金属学及工艺—铸造]