Computation of synthetic surface heat transfer coefficient of 7B50 ultra-high-strength aluminum alloy during spray quenching

According to inverse heat transfer theory, the evolutions of synthetic surface heat transfer coefficient (SSHTC) of the quenching surface of 7B50 alloy during water-spray quenching were simulated by the ProCAST software based on accurate cooling curves measured by the modified Jominy specimen and temperature-dependent thermo-physical properties of 7B50 alloy calculated using the JMatPro software. Results show that the average cooling rate at 6 mm from the quenching surface and 420-230 C-degrees (quench sensitive temperature range) is 45.78 C-degrees/s.The peak-value of the SSHTC is 69 kW/(m(2)center dot K) obtained at spray quenching for 0.4 s and the corresponding temperature of the quenching surface is 160 C-degrees In the initial stage of spray quenching, the phenomenon called "temperature plateau" appears on the cooling curve of the quenching surface The temperature range of this plateau is 160-170 C-degrees with the duration about 3 s. During the temperature plateau, heat transfer mechanism of the quenching surface transforms from nucleate boiling regime to single-phase convective regime.