Wettability and Interfacial Heat Transfer During Solidification of Al-Si Alloy (A413) Melt Droplets on Metallic Substrates

Wetting and heat transfer during solidification were studied with Al-Si alloy (A413) melt droplets on copper and stainless steel cylindrical substrates. As the molten metal cools down and solidifies, the interface changes from the initial liquid/solid contact to solid/solid contact, leading to variations in the rate of interfacial heat transfer. The effect of substrate roughness and melt superheat on the droplet contact angle and heat flux was investigated. A smooth substrate surface resulted in higher casting surface roughness, and the contact angle of solidified droplets increased with an increase in substrate roughness. Surface profile analysis indicated the presence of an air gap between the substrate and solidified droplet. The gap width was used to determine the variation of heat transfer coefficient (HTC) along the radial direction of the substrate surface at the end of solidification. Deformation of the solidified droplet was inverse for copper versus stainless steel resulting in an increase in HTC for copper and a decrease for stainless steel.