Characterization of Heat Transfer Coefficient of Lightweight Alloys in Kirksite Dies

The heat transfer coefficient (HTC) is an important parameter in the finite element (FE) modelling of warm and hot forming operations. The HTC, among other parameters, governs the FE model predictions for the cooling rate within the blank and the resulting constitutive behaviour and formability. In the current work, the HTC of two aluminum alloys (AA5182-O and AA7075-T6) and one magnesium alloy (ZEK100) is characterized. Blanks were heated in a convection furnace and subsequently quenched in a set of kirksite dies under various contact pressures. Kirksite is a zinc-based alloy commonly used in prototype tooling. The temperature-time (T-t) profile of the blanks and die were measured during each quenching experiment. The resulting T-t profiles were input into a Matlab script, which calculated the HTC using an iterative regression technique. (paper)