Study on the interfacial heat transfer coefficient between AZ91D magnesium alloy and silica sand

In this investigation, a simple and feasible cylindrical geometry was selected for determination of interfacial heat transfer coefficient (IHTC) between AZ91D magnesium alloy and silica sand mold. IHTC was calculated by inverse method based on the experimental data. Calculating results show that IHTC experiences three distinct variation stages as a function of casting surface temperature (Tcs) during mushy zone region. When Tcs is between 595 °C and 593 °C, IHTC decreases rapidly from 525 W/(m2 K) to 410 W/(m2 K) due to the onset of air gap; When Tcs is between 593 °C and 554 °C, as well as solid fraction of casting center lower than critical solid fraction (CSF), IHTC decreases slowly for the durative feeding of liquid metal to casting surface; When Tcs is between 554 °C and 470 °C, as well as solid fraction of casting center higher than CSF, IHTC decreases rapidly to a constant value of 62 W/(m2 K) for the absence of feeding. The same solidification process was simulated by Anycasting™ software and the cooling curve of the casting surface was obtained using the inverse-calculated IHTC as a function of Tcs. It is observed that the absolute values of ΔT errors of the measured cooling curve and the calculated cooling curve fluctuate from 0 °C to 7.5 °C, proving the accuracy of the calculated IHTC by using inverse method.