Microstructure, Tensile and Fracture Behaviors of Squeeze Cast Wrought Mg Alloy AZ80

Wrought magnesium alloy AZ80 with a thick section of 20 mm was prepared by squeeze casting (SC) and permanent steel mold casting (PSMC). The porosity measurements of the SC and PSMC showed that the SC AZ80 had a porosity of 0.52%, which was the 77% lower than that (2.21%) of the PSMC counterpart. The microstructure analyses and phase identification indicated that the cast AZ80 alloy consisted of a primary α-Mg phase, eutectic Mg-Al-Zn phases and Al-Mn intermetallic. The fine primary α-Mg dendrites and a high amount of the intermetallic phase were present in the SC AZ80 alloy. The yield strength (YS), ultimate yield strength (UTS), elongation (ef), elastic modulus (E) and strain hardening rate of the cast AZ80 specimens were evaluated by tensile testing. The measured engineering stress versus strain curves showed that the SC AZ80 alloy exhibited 84.68 MPa in YS, 168.23 MPa in UTS, 5.07% in ef, and 25.1GPa in modulus while the YS, UTS and ef of the PSMC specimen were only 71.61 MPa, 109.04 MPa, 1.85% and 21.9GPa. The calculated resilience and tensile toughness indicated that the SC AZ80 was more capable of resisting energy loads in elastic deformation and had an ability to absorb energy during plastic deformation than that of the PSMC AZ80. Also, the analyses of the true stress versus strain curves revealed that, upon the onset of plastic deformation, the strain-hardening rate of the SC AZ80 sample was 10,341 MPa, which was 9% higher than that (9,489 MPa) of the PSMC AZ80 specimen. The obtained mechanical properties showcased the fit of the casting process to wrought magnesium AZ80 alloy, which was squeeze casting. The low porosity level, fine dendritic structure and a high content of intermetallic phase should be somewhat responsible for high mechanical properties of the SC AZ80 alloy.