Investigation of the Effect of Various Ca Content on Microstructure and Mechanical Properties of As-cast ZK60 Magnesium Alloys

Abstract

The effect of various Ca content on microstructure and mechanical properties of as-cast Mg-6Zn-0.5Zr (wt.%) Mg alloys with hot tensile testing at 345°C were investigated. The alloy was produced with the LPDC method [1]. Microstructural characterization as-cast alloy demonstrated that wt.% Ca content increase, grain size decreases till wt.% 0.8Ca, the further increase affects gradual change in grain size to ~60 µm at 345°C. Therefore, increase in Ca ratio from 0.4 wt% forming to strip-like Mg-Zn intermetallics at grain boundaries, Ca-Mg-Zn ternary phase at grain boundary corners. Dramatical decrease in yield and tensile strength at wt% 1.6Ca addition is 37.6 MPa and 39.7 MPa respectively which is relatively low at 345°C due to the absence of retarded DRX'ed small particles prohibited the grain growth after the TMT process. Conversely, elongation-to-fracture increases were observed as 1.26 at 345°C showing the temperature-dependent texture softening results in improvement of mechanical properties. Wear rate is also affected from wt.% Ca addition so the gradual increase up to 1.2 wt% Ca is 3.70 x 10 -3 mm 3 /m. Similarly, a gradual increase in hardness values was obtained with Ca addition in ZK60 alloy. In this study, the effect of temperature-dependent Ca addition (wt %) on gradual enhancement in mechanical properties was observed at as-cast magnesium alloys.