An Application of Injection Molding to Semisolid Processing of Metallic Alloys: A Role of SIMA in Feedstock Transformation

Abstract

Injection molding has proven for over 150 years to be the efficient mass manufacturing technology of net-shape components from plastics, however, its application to metallic alloys, despite four decades of commercialization, still creates challenges. Although early designs assumed a direct replacement of plastic with magnesium, subsequent research revealed essential differences in machinery and processing requirements, imposed by metallic alloys. The key discovery revealed that the dendrite-to-globule transformation during coarse particulate melting is caused by strain induced melt activation (SIMA) due to feedstock deformation imposed at their manufacturing stage, not due to the injection screw shearing during processing. As a result, the process control parameters and the screw and barrel design can be optimized with a focus on other screw functions. That discovery also led to the simplified machinery designs, eliminating the complex injection screw, and replacing it with a simple plunger.