Effects of melt treatment temperature and isothermal holding parameter on water-quenched microstructures of A356 aluminum alloy semisolid slurry
(1. State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China;
2. Key Laboratory of Nonferrous Metal Alloys and Processing, Ministry of Education, Lanzhou University of Technology, Lanzhou 730050, China)
Abstract: The semisolid slurry of the A356 aluminum alloy was prepared by self-inoculation method (SIM), the effects of melt treatment temperatures and isothermal holding parameters on water-quenched microstructures of A356 aluminum alloy semisolid slurry were investigated, and the solidification behavior of the remaining liquid phase (secondary solidification) was analyzed. The results indicate that the melt treatment temperature has significant effects on the final semisolid microstructures. The semisolid slurry which is suitable for the rheological forming can be produced when the melt treatment temperature is between 680 and 690 °C. During the isothermal holding process, the growth rate of the primary particles conforms to the dynamic equation of Dt3-D03=Kt, and the coarsening rate of the primary particles is the fastest when the isothermal holding temperature is 600 °C. Additionally, the isothermal holding time also has obvious effect on the secondary solidification microstructures. The secondary particles are the smallest and roundest when the isothermal holding time is 3 min. The amount of the secondary particles gradually increases with the increase of isothermal holding temperature, and the eutectic reaction therefore is confined into small intergranular areas, contributing to the compactness of the final solidified eutectic structures.
Key words: aluminum alloy; semisolid; self-inoculation method; secondary solidification; primary particles; eutectic structure