Investigation of Mechanical Properties of Biodegradable AZ31 Magnesium Alloys with Calcium Addition

Abstract

In this research, the mechanical properties of as cast AZ31 magnesium alloys were investigated after adding 0.3 and 0.6 wt.% of calcium. As cast ingots of AZ31 Mg alloys with 0.3 and 0.6 wt.% of calcium were prepared under Argon environment. The specimens were made according to ASTM standards to perform tensile, compressive, and hardness tests. The microstructure and surface morphology of the alloys were analyzed using the images obtained from the optical microscope and scanning electron microscope (SEM) + EDAX. The yield strength (YS), ultimate tensile strength (UTS), ultimate compressive strength (UCS), percentage elongation, and Brinell hardness (HB) of these biodegradable Mg alloys were found. The addition of calcium to as cast AZ31+x wt.% Ca magnesium alloys (x =  0, 0.3 and 0.6) imparts good grain refinement and improves the mechanical properties with the formation of β-Mg₁₇Al₁₂ and Mg₂Ca intermediate metallic phases. The addition of calcium highly resists the formation of oxides and increases the strength of the alloy with fewer casting defects. The experimental results show that the yield strength increases up to 3.5 times with the increase of Ca content in AZ31 Mg alloys. The UTS is found up to 24 % with Brinell hardness showing an increase up to 53.3 %. The elongation increases from 10.5 % to 18 % with the addition of 0.3 wt.% of Ca but decrease to 12 % at 0.6 wt.% Ca. The mechanical properties and microstructure analysis of AZ31 + x wt.% Ca alloys prove their compatibility for making orthopedic implants in human bone surgery.