Date of Award

12-19-2023

Publication Type

Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

Keywords

AZ31;Light Metals;Magnesium Alloys;PEO Coating;PSMC;Squeeze Casting

Supervisor

Henry Hu

Rights

info:eu-repo/semantics/embargoedAccess

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Abstract

Wrought magnesium alloy AZ31 with a thick section of 20 mm was prepared by squeeze casting (SC) and permanent steel mold casting (PSMC). SC AZ31 had a porosity of 1.13%, which was 57% lower than that (2.66%) of the PSMC AZ31. The microstructure analyses phase identification indicated that cast AZ31 alloy consisted of a primary α-Mg, eutectic Al-Mg-Zn, and Al-Mg-Mn intermetallic phases. SC AZ31 had a higher amount of intermetallic phase. The yield strength (YS), ultimate yield strength (UTS), elongation (ef), elastic modulus (E) and strain hardening rate of the cast AZ31 specimens were evaluated by tensile testing. SC AZ31 alloy exhibited 60.8 MPa in YS, 194.3 MPa in UTS, 13.8% in ef, and 36.2 in modulus. While the YS, UTS, and ef of the PSMC AZ31 specimen were only 49.5 MPa, 173.1 MPa and 9.2% respectfully. The calculated resilience and tensile toughness indicated that the SC AZ31 was more capable of resisting energy loads in elastic deformation and had an ability to absorb energy during plastic deformation without fracture than that of the PSMC AZ31. The true stress versus strain curves revealed that, upon the onset of plastic deformation, the strain-hardening rate of the SC AZ31 sample was 7,400 MPa compared to 6,700 MPa for PSMC AZ31. Application of PEO coating reduced tensile properties of UTS, YS ef, toughness and resilience from 194.3 MPa, 60.8 MPa, 13.8%, 17.6 MJ/m3 and 51.1 kJ/m3 to 162.8 MPa, 38.7 MPa 9.3%, 9.4 MJ/m3 and 19.2 kJ/m3 respectively. Elastic modulus of the SC AZ31 was increased by the PEO coating from 36.2 to 38.5 GPa. The PEO coating reduced the strain-hardening rate of SC AZ31 at the onset of plastic deformation from 7200 MPa to 5800 MPa. Thus, limited strengthening capability of the SC AZ31 to the extended plastic deformation before failure.

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