Effect of Initial Microstructure on Mg Scroll Forging under Warm Forming Condition

Abstract

Magnesium (Mg) alloys have attracted considerable interest for various applications, including those in the automotive and electronics industries, because of their high specific strength, excellent thermal conductivity, and recycling capability in comparison with commonly used aluminum alloys and steels for structural materials. One of the core parts in the compressor unit of an automobile is the scroll rotor, which is assembled with two scrolls, a rotating orbit scroll on the fixed scroll, to compress the refrigerant. In this study, we proposed a net-shape forging process and an apparatus with the back-pressure technique for the Mg scroll at a forging temperature of 350 degrees C with an Mg-6Al-1Zn extruded billet. The optimum amount of back-pressure is calibrated by finite element analysis using DEFORM-3D, which enhances the wrap height distribution in the Mg scroll uniformly. To elucidate the effect of the initial texture on the forgeability of the Mg scroll, twin-induced and dynamic recrystallization (DRX)-induced specimens are applied in Mg scroll forging, where the formability of the Mg scroll with the DRX-induced specimen is found to be noticeably improved in terms of the wrap height.