Heat Transfer Behavior During Water Spray Quenching of 7xxx Aluminum Alloy Plates

Abstract The desired microstructure and mechanical properties of heat treatable 7xxx aluminum alloy can be achieved after spray quenching by controlling spray parameters. However, heat transfer behavior between specimen and quenchant is transient and complicated in quenching process. In this paper, a spray quenching system was utilized to quench for 7xxx aluminum alloy. The influence of spray parameters, including spray pressure and spray distance, on heat transfer behavior was examined and discussed. Heat flux (HF) and heat transfer coefficient (HTC) were calculated by iterative method. The results indicated that the aluminum alloy experienced transition boiling, nucleate boiling, and convection cooling regimes during spray quenching process. Heat transfer capability first increased and then decreased with the increasing of spray pressure or spray distance. A function of local heat transfer coefficient (L-HTC) which is variable in specimen surface temperature, spray parameters, and spatial location was constructed. Residual stress of 7xxx aluminum alloy plates was increased first and then slightly differed with the increase of volumetric flux.