Observation of interface of two kinds of bi-metal composite parts prepared by thixo-forging
(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China;
3. Baotou Aluminium Co. Ltd., Baotou 014046, China)
2. School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China;
3. Baotou Aluminium Co. Ltd., Baotou 014046, China)
Abstract: Two kinds of bi-metal composite parts (Sn-15%Pb and Pb-22%Sn bi-metal system, and Al-7%Si and SiCp/6061 MMC bi-metal system) were prepared by the strain-induced melt activated thixo-forging. The interfaces of the bi-metal composites were observed by OM and SEM. The observations show that the semisolid metals keep independence during thixo-forging. The solid phases in the semisolid slurries maintain their original morphologies after thixo-forging. The liquid phases near the interface mix together and form a thin layer. The interfaces are bonded firmly with the metallurgical bonding. No oxide layers are found at the interfaces. Strengths of the interfaces were investigated by the micro-hardness test. The experimental results show that the composite interfaces have high strength. However, the agglomerated enhancing particles cause fine defect on the interface of the Al-7%Si and SiCp/6061 MMC bi-metal composite.
Key words: semisolid metal processing; bi-metal composite; thixo-forming, die-forging; metal matrix composite