Effect of Pressure on Microstructure and Mechanical Properties of Squeeze Casting Mg-6Zn-1Al-0.5Mn-0.5Ca Alloy

Abstract

The effect of pressure of squeeze casting on the microstructure and mechanical properties of Mg-6Zn-1Al-0.5Mn-0.5Ca alloy has been systematically studied using XRD. SEX. TEM and tensile test. The results show that the microstructure of the as-cast alloy consists of α-Mg matrix with τ(Mg32(Al, Zn)49) and some Al8Mn5 second phase particles. The imposed pressure dose not change the composition of alloy phase precipitation. With the increase of squeeze casting pressure, the second phase particles of the as-cast ZAMX6100 alloy becomes more and fine, and more uniformly distributed. Simultaneously, ZAMX6100 alloy solidified under pressure improves the uniform distribution of micro-elements Mn, Ca, which decreases the extent of interdendritic segregation. When pressure is increased from 0 MPa to 100 MPa, the tensile strength, yield strength, elongation and hardness of ZAMX6100 alloy are all improved by 27%, 14%, 31% and 9% respectively. The fine ZAMX6100 alloy microstructure is mainly caused by the atom spread activation energy decreasement under pressure during the solidification, which decreases the crystal growth velocity, and at the same time the high pressure squeeze casting causes an entire contact of magnesium alloy with the mold inside, which causes the increase of cooling rate and refinement of microstructure.

Keywords

• squeeze casting pressure
• second phase
• Mg-Zn-Al-Mn-Ca alloy
• interdendritic segregation
• dispersion