Semi-solid forming is a relatively new process whereby an alloy with thixotropic characteristics at a temperature between solidus and liquidus is cast into a component in a mould. By not starting with a superheated melt as in conventional liquid pressure die casting, semi-solid processing offers distinct advantages such as low cycle time, less porosity because of non-turbulent flow, improved die life and significantly better mechanical properties. This paper describes results of work related to the preparation of AZ91D fedstock by electro-mechanical stirring with superheat reduction, reheating of this material to the thixotropic state by induction and semi-sloid die casting a number of complex box-like components. The microstructure was monitored throughout the processing to achieve the desired semi-solid microstructure for successful die casting. The optimal casting parameters (metal temperature, ram velocity and metal pressure) for die casting the box-like components are given. It also presents the results for the optimized heating of the feedstock material in the form of 76 mm diameter and 152 mm long billets. The microstructure of feestock consists of rosettes of primary alpha phase that becomes globular after reheating to 580 degC. Results of the casting trials demonstrate that semi-solid die casting requires a much more precise controll of the billet temperature and a well-defined window of castability for the alloy cast.
Production and die casting of semi-solid magnesium alloy AZ91D
Herstellung und Druckgießen der flüssig-festen Magnesiumlegierung AZ91D
2002
6 Seiten, 9 Bilder
Conference paper
English
Production and Die Casting of Semi-Solid Magnesium Alloy AZ91D
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