The Study Of Semi-Solid Thixo-Process Of AZ91D Magnesium Alloys

Semi-solid metal process (SSP) process is a new near net shape technology. And its drip molding is compaction, high mechanical property, little machining and complex. So, it is more and more taken into account in all over the world. Because molten of magnesium alloys are easy to burn, magnesium alloys are difficult to conventional process and control quality. Since SSP was applied on magnesium alloys, it had settled the key puzzle. This paper used Strain-Induced Melt Activation (SIMA) to prepare the semi-solid blank of AZ91D magnesium alloys, and researched the shear-rheology property and the fluxion property of thixo-process with AZ91D magnesium alloys by experiment. This paper researched the refining and spheroidization mechanics of the semi-solid grains of AZ91D magnesium alloys by SIMA. It analyzed the effect of cool plastic deformation ratio, semi-solid temperature and holding time on microstructure of semi-solid blank. The results indicate that: under this experiment condition, the best processing parameters of the semi-solid blank preparation of AZ91D magnesium alloys are cool plastic deformation ratio 7%～9%, semi-solid temperature 570±5℃, holding time 20min～30min. This paper studied the shear-rheology property of semi-solid thixo-processing of AZ91D magnesium alloys by home-made mould. It analyzed the effect of the shear-rheology property in semi-solid state on different holding time at 570℃. The results indicate that: under this experiment condition, the best processing parameters are isothermal reheating temperature 570℃, holding time 30min. At the same time, based on the phenomenon and data of experiment, it established the semi-solid rheologic module of AZ91D magnesium alloys: H1—(N1/H2)—(N2/S). In order to acquaint the fluxion property of thixo-processing of AZ91D magnesium alloys, this paper used home-made mould to test the fluxion property at 570℃. This paper analyzed the effect of fluxion property on different holding time, and disclosed the fluxion mechanics of AZ91D magnesium alloys in semi-solid state, and obtained the best processing parameters under this experiment condition: isothermal reheating temperature 570℃, holding time 30min～45min. At the meantime, this paper analyzed the tension property of the thixo-processing drip molding of AZ91D magnesium. The results indicate that: the tension property of thixo-processing drip molding is better than convention processing drip moldings'.