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The interfacial heat transfer coefficient (HTC) between the steel mold and AZ91D magnesium (Mg) alloy that cast under various initial solid fractions were investigated in this study.The interfacial HTC was determined by using an Inverse Method with measured temperature data and known thermo-physical properties. A Computer Aided Cooling Curve Analysis technique was used to determine the solid fraction versus temperature relationship. To comply with the requirements of the Inverse Method, a one-dimensional heat transfer system from the casting to the mold was designed for the permanent mold casting of AZ91D Mg alloy in molten and semisolid states.Experiments were conducted with different initial solid fractions of 0, 30, and 50%. The results indicate that the HTC profile of molten AZ91D during solidification can be divided into five stages, while casting with semisolid AZ91D only into three. During each stage, the casting/ mold interfacial conditions vary, which in turn causes the HTC values to vary. These data are critical for any solidification model of permanent mold casting and semisolid casting to obtain a reliable prediction of the thermal profile inside the solidifying casting and its freezing time.

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A three-dimensional simulation system of sputter deposition for microstructure evolution of thin films has been developed in this study. In terms of the nucleation stage, the nucleation process is modeled using a randomization method, which produces atomic data to describe the condition of nuclei coverage. In terms of the growth stage, the topographic evolution is modeled using level set methods, and the deposition rate is evaluated considering shadow effects. The effects of controlled nucleation variables (including sticking coefficients, captured radii of clusters and critical nuclei size) on nucleation types are discussed in the model as well as the influences of nucleation types on the following grain growth. The simulation results show that three different nucleation types (networks, flat pieces and islands) are observed for different combinations of controlled nucleation variables. Under the assumption of immobile grain boundaries, the resulting grain shapes and grain structures of these three nucleation types are different. The simulation results of nucleation and growth are also shown to be consistent with the experimental data of references.