A Comparative Study on the Microstructure, Mechanical Properties, and Hot Deformation of Magnesium Alloys Containing Zinc, Calcium and Yttrium

Some magnesium alloys are considered as biocompatible materials because they are biodegradable or bioabsorbable in body fluids without causing health hazards. Zinc (Zn) and calcium (Ca) are essential micronutrients in the body and their bio-absorption is beneficial when an orthopedic implant made of magnesium alloy corrodes in a controlled manner. Yttrium (Y) in small quantity can be added to improve the mechanical properties. Cast alloys are hot worked to obtain wrought microstructures so as to develop components of superior and consistent properties. In this study, the microstructure, mechanical properties, and hot deformation behavior of four cast magnesium alloys containing zinc, calcium and yttrium in different combinations are compared. It is found that calcium is an excellent grain refiner whereas yttrium enormously increases the grain size. While all these elements provide strengthening, calcium is found to be the most effective one in combination with zinc and yttrium or zinc alone. The hot working behaviors of these alloys over broad ranges of temperature and strain rate are compared using processing maps. Mg–1Zn–1Y alloy exhibits higher level of workability compared to the other alloys and over entire strain rate range of 0.0003–10 s⁻¹ and 460–540 °C, although the initial grain size of the cast alloy is extremely large.