HEAT TRANSFER AT CASTING/MOLD INTERFACE IN PRESSURIZED SOLIDIFICATION OF AL ALLOY A380
Aluminum alloy A380 is widely used for various automotive components made by high pressure die casting (HPDC) process. The HPDC A380 has moderate mechanical properties due to its relatively high porosity content. It has demonstrated that squeeze casting (SC) is capable of eliminating porosity and improving the mechanical properties of A380. But, studies on heat transfer phenomena occurring during squeeze casting of
A380 are limited. In this study, a step die was made by P20 steel for squeeze casting aluminium alloy A380 with five different section thickness of 2, 4, 8, 12, and 20 mm under an applied pressure of 90 MPa. K-type thermocouples were employed to measure temperatures of the squeeze casting surface as well as three different depths, i.e., 2, 4, and 8 mm from the die inner wall at each step. With the temperature measurement, interfacial heat transfer coefficients (IHTC) at the casting and die inner surface and pertinent heat fluxes were determined
by solving one-dimensional heat conduction formula using the inverse method. The results of the calculated IHTCs showed that, upon the commencement of squeeze casting, the IHTC values for all the 5 steps rose rapidly. Before decreasing, the IHTC at each step reached its individual pinnacles. As the section step thickness changed from 2 mm (step 1) to 20 mm (step 5), the IHTC peak values increased significantly. It took longer time for a thicker step to attain its peak IHTC value, and also to decrease its IHTC values to a lower steady level.