Study On High Pressure Solidification And Heat Compression Behavior Of Mg_95.50Zn_3.71Y_0.79Alloys

The experimental alloy of this research was Mg95.50Zn3.71Y0.79 alloy,prepared by 2RRL-M8 vacuum furnace resistance and the high-pressure solidification process was conducted using the CS-IB cubic press at 2 GPa and 4 GPa.Then thermal compression behavior experiments of the alloy was conducted using Gleeble-3500 thermal simulation testing machine at the temperature from 250 to 400?,and the strain rate ranged from 0.001 to 1.0 s-1.Then the post-deformation microstructure were observed and analyzed to study the thermal compression behavior of the experimental alloy.The results show that:the conventional casting microstructure of the Mg95.50Zn3.71Y0.79 alloy consisted of the matrix ?-Mg,I-Mg3Zn6Y and W-Mg3Zn3Y2 phases while the eutectic second phase distributes among the coarse dendrites in the form of continuous net shape.While microstructure of the 4 GPa high pressure solidified alloy was significantly refined:number of the ice flake-shaped dendrite groups in the 100 ?m range increased from 6 to 110.And the microstructure of high-pressure-solidified Mg95.50Zn3.71Y0.79 alloy mainly consisted of the ?-Mg matrix,I-Mg3Zn6Y and Mg24Y5 phases,and the second phase was no longer network-shaped,while it was mostly "rod" or"dot" shaped,evenly dispersing in the matrix,and the volume fraction of the second phase reduced from 21%to 13%,by 38%.Besides microstructure refinement,thermal deformation properties of this alloy was also improved.In condition of high strain rate and deformed at 250?,the ?p of the high pressure solidified alloy was up to 233 MPa,60 MPa higher than the conventional casting alloys.At high strain rate,high pressure solidified alloys showed a plausible work hardening ability,the twinning density was high during work hardening,and there was evident slippage.The post-deforming microstructure showed thermal compression process undergone significant dynamic recrystallization,and the dynamic recrystallization volume fraction increased with strain rate.The refined microstructure and the dot-shaped second phase of the high pressure solidified alloy contributed to the dynamic recrystallization.High pressure solidified alloys underwent uniform deformation,and the dynamic recrystallization volume fraction is much higher than that of the conventional casting alloys.And at 300 ?,this alloy almost underwent complete dynamic recrystallization state.The plastic deformation constitutive equations of the high-pressure solidification and conventional casting alloys were respectively:...