Investigation of the Effect of Inert Gas Bubbling Semi-Solid Process on the Microstructure and Mechanical Characteristics of AZ91 Magnesium Alloy

Small and uniform globular grains are produced by purging inert gas bubbles into the melt in a semi-solid process. The influence of argon gas bubbling has been investigated on the microstructure and mechanical properties of AZ91 magnesium alloy. The solidification parameters like liquidus and solidus temperature and the solid fraction have been determined using the thermal analysis technique. The process's fundamental parameters are the gas flow rate, gas purging temperature, and duration of gas injection. Among these parameters, the gas flow rate significantly affected the microstructure. The image analysis showed that inert gas bubbling treatment could acquire fine and spherical semi-solid slurry. At the optimum condition of 4 L min(-1) gas flow rate at 610 & DEG;C for a period of 10 s, the primary & alpha;-Mg particles have a mean diameter of 58.4 & mu;m and a mean shape factor of 0.75. The results showed that by performing the inert gas bubbling at the optimum condition in the semi-solid process, yield strength, ultimate strength, and elongation of AZ91 alloy are improved by 17%, 25%, and 190%, respectively, compared with conventional casting. Mechanical properties have been enhanced because of the spheroidizing and refinement of primary & alpha;-Mg, reduction of gas porosity and good distribution of eutectic phases during solidification.