Experimental and Stochastic Modeling of the Globular Microstructure and the Microsegregation Evolution during the Solidification of Magnesium Alloys Cast at Low Superheat via Containerless Melting

摘要

Casting at low superheat has a strong influence on the solidification morphology and macro- and micro-structures of cast alloys. This paper shows the micro-structure and microsegregation of cast Mg AZ31B alloy at superheat of 5℃, summarizes the multiscale model, and describes the simulation results obtained with a previously developed stochastic mesoscopic solidification model capable of predicting the microstructure of the cast alloy. The simulation results are compared with casting experiments carried out using the Magnetic Suspension Melting process. Casting at this low superheat was found to produce castings with a fine globular grain structure, with an average grain size of about 80 μm, which is about one-third the size of that obtained by conventional casting techniques. The stochastic model was validated against the experimental measured grain structure and Al microsegregation. A parametric study was performed to determine some key material and process parameters related to processing of cast Mg AZ31B alloy.