铝镁包覆挤压材料界面微观组织与力学性能研究  

Microstructure and Mechanical Properties of Interfaces of Extruded Cladding Mg-Al Rods

作　　者：乔及森[1] 聂书才[1] 张涵[1] 赵文军[1] 夏天东[1] 

机构地区：[1]兰州理工大学省部共建有色金属先进加工与再利用国家重点实验室,甘肃兰州730050

出　　处：《稀有金属》2015年第6期481-486,共6页Chinese Journal of Rare Metals

基　　金：甘肃省科技重大专项项目(1203GKDJ004);甘肃省青年科技基金项目(1308RJYA046)资助

摘　　要：采用反向挤压技术将AZ31镁合金和纯铝材料在不同温度下挤压形成包覆棒材。挤压过程中纯铝包覆在镁合金外侧,镁铝间形成冶金结合界面,实现了镁铝双金属的复合。挤压完成后使用光学显微镜(OM)、扫描电子显微镜(SEM)及能谱(EDS)分析技术对镁铝包覆挤压合金进行了组织及力学性能分析,重点研究了铝镁合金结合界面处化学成分过渡及相结构的演化与分布,同时采用显微硬度计测试了镁铝结合界面的显微硬度。结果表明,通过反向热挤压工艺可以得到表面光洁、无明显缺陷的铝镁合金包覆挤压制品。在高温高压条件下,镁铝复合金属在界面结合区发生了元素扩散,铝镁合金浓度出现明显的梯度变化,进而在结合界面上发生冶金反应,形成约350μm厚的金属间化合物层,物相分析表明在靠近镁合金基体一侧生成富镁相Al12Mg17,靠近纯铝一侧生成富铝相Al3Mg2,主要为脆性相生成。沿包覆棒材横截面直径方向从边部到芯部进行显微硬度测试,结果表明,该合金包覆型材具有明显的力学不均匀性,在铝镁结合界面处的硬度高于两侧基体材料,其峰值硬度可达HV 200以上,包覆型材在结合界面的组织差异和强度、硬度失配导致结合界面的力学性能急剧弱化,容易产生开裂。The rods of aluminum cladding magnesium alloys AZ31 were fabricated by cladding extrusion at different temperatures. During the process, the AZ31 magnesium alloys were coated by the aluminum. The composite, with bonding interface between alumi- num and magnesium forming, was obtained. After the extrusion process, the microstructure evolution and mechanical properties of the cladding materials were analyzed by the optical microscope （OM）observation, scanning electronic microscopy （SEM） and energy dis- persive spectrometer （EDS） tests. Emphasis was put on the microstructure and chemical composition distribution of the interface be- tween aluminum and magnesium. Meanwhile, the microhardness was tested. The resuhs showed that qualified products with smooth surface and no obvious defects could be made by extrusion. Elements diffusion in the composite layer occurred during the extrusion process, which caused a change of gradient of the element concentrations. An intermetallic layer was formed with thickness of 350 ~m. Phase identification showed that the magnesium-rich phase close to the side of magnesium alloy was Al12Mg17 and the aluminum-rich phase close to the aluminum side was A13 Mg2 , which were all brittle phases. Therefore, the hardness of Mg-A1 bonding interface could be up to HV 200 or more compared to that of base metals. The inhomogeneous properties of the interface for the extrusion profiles caused poor load ability and the cracks to occur in the composites.

关 键 词：AZ31镁合金 纯铝 包覆技术 反向热挤压 微观组织 

分 类 号：TG379[金属学及工艺—金属压力加工] TG146.2[一般工业技术—材料科学与工程]