Papers by Keyword: Squeeze Pressure

Abstract: A semisolid slurry of Mg_98.5Ni_0.5Y_1.0 alloy was prepared by UV (ultrasonic vibration) method, then the slurry was cast under different squeeze pressures, in which the pressure varied from 0 MPa to 400 MPa. The results show that the primary α-Mg phase and LPSO structure (Long Period Stacking Ordered structure) of the alloy can be refined significantly. The solid solubility of Y and Ni elements in magnesium matrix can be increased with higher pressure, and the Mg₂Ni particles is also precipitated out in LPSO structure under pressure. The grain size is decreased with the enhancement of squeeze pressure, which improves the strength. The alloy squeeze cast under pressure of 100 MPa has the highest cost performance. Its yield strength, tensile strength and elongation are 115 MPa, 243 MPa and 13.5%, and they are increased by 21.5%, 9.0% and 16.4% respectively compared with the alloy without applied pressure.

Abstract: The long period stacking ordered (LPSO) phase reinforced Mg alloys have received many researches in recent years because of their excellent mechanical properties. However, the LPSO phase usually concentrates at the grain boundaries with a coarse network structure, which seriously deteriorates its strengthening effect. In this research, rheocasting and ultrasonic vibration (USV) process were firstly used to refine the LPSO phase in Mg alloy. The semisolid slurry of Mg96.9Y2Zn1Zr0.1 (at.%) alloy was prepared by USV and then formed by rheo-squeeze casting (RSC). The effects of USV and squeeze pressure on the microstructure and mechanical properties of this Mg alloy were investigated. The results show that the primary α-Mg and coarse LPSO phases were refined obviously by USV and RSC. The tensile strength and elongation of the RSC Mg96.9Y2Zn1Zr0.1 alloy were 232 MPa and 17.7% respectively, which were increased by 17.8% and 172.3% respectively compared to the conventional liquid casting alloy. The refinement mechanism of the LPSO phase in semisolid Mg alloy is also discussed.

Abstract: A functional automotive part, reaction shaft support, was fabricated by local squeeze and vacuum Diecasting (LSVD) with light-weight Al-15%Si hypereutectic alloy which has good fluidity and excellent wear resistance. The effects of local squeezing pressure and time-lag of LSVD process on the microstructure of the product were investigated. Measurement of specific gravity with the change of local squeeze pressure and time-lag showed that the local squeezing effect can be increased by increasing squeeze pressure and decreasing time-lag. However, too high a squeeze pressure and too a low time-lag brought about insufficient squeezing effect due to instant movement to the squeeze plunger stroke end point. Through the combination of vacuum suction before melt injection and local squeezing after melt injection in LSVD process, light-weight Al-15%Si alloy reaction shaft support was successfully developed, resulting in excellent microstructural and mechanical properties