Melting behavior of magnesium alloy chips in thixomolding process
(1. Institute of Materials Science and Engineering, Changchun University of Technology, Changchun 130012, China;
2. R&D Centre, Foundry Corporation, FAW Group Corporation, Changchun 130062, China;
3. Key Laboratory of Automobile Material, Ministry of Education, Jilin University, Changchun 130025, China)
2. R&D Centre, Foundry Corporation, FAW Group Corporation, Changchun 130062, China;
3. Key Laboratory of Automobile Material, Ministry of Education, Jilin University, Changchun 130025, China)
Abstract: The samples were fabricated by 220 t thixomolded machine made by Japan Steel Works. The microstructure from the AZ91D magnesium alloy chips to the thixomolded products was investigated. Melting behavior of the chips in thixomolding process was analyzed. The evolution processing of solid phase morphology was studied, and evolution model was put forward. The results show that microstructures in outer zone of a chip and the inner zone are obviously different, and the severe distortion takes place in the brim of the chip, where the grains are observed to be bent, distorted, even broken. The severe plastic deformation region is firstly molten, then segregation area in the inner of the chip continues to melt. The liquid phase in solid phase does not formed by liquid entrapped during shearing process, but primarily induced by internal composition segregation.
Key words: AZ91D magnesium alloy; thixomolding; chips; melting behavior