Alloy Transformations During Molding
The unique microstructure of injection molded alloys is created as a result of multiple transformations that take place during the flow of material through the machine barrel, followed by injection into the mold cavity and final solidification. While for die casting and some semisolid technologies the microstructure evolution is quite well described, for semisolid molding, the role of processing parameters is still being researched. In particular, the contribution of shear imposed by the injection screw remained for a long time a matter of controversy. This is in part due to the uniqueness of injection molding, which does not allow for the direct adoption of phenomena and mechanisms common for other semisolid techniques. First, as opposed to the majority of semisolid processes, which rely on the formation of the thixotropic structure during solidification, during injection molding the globular features are predominantly created at the stage of melting. Second, the feedstock represents a specific form of an alloy whose microstructure is modified during conversion into small particulates by mechanical or thermal methods.
KeywordsInjection Molding Solid Fraction High Solid Content Semisolid State Semisolid Slurry
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