Effect of initial quenching temperature on the hardness of AA6061 aluminium alloy and C18200 copper alloy

Abstract

This study presents a quantitative investigation of the quench sensitivity of AA6061 aluminium and C18200 copper alloys under controlled water and oil quenching across an initial temperature range of 20–80?°C. Specimens were solution-treated according to ASM-recommended procedures, followed by rapid transfer to agitated quench baths to ensure turbulent cooling. Brinell hardness measurements revealed that aluminium exhibited a pronounced decrease in hardness with increasing quench temperature, while copper showed comparatively minor changes. The Quench Sensitivity Index (QSI), calculated as the hardness loss per degree Celsius, confirmed aluminium’s higher practical sensitivity (0.283–0.405?HB/°C) relative to copper (0.152–0.183?HB/°C). Statistical analysis using ANOVA indicated that temperature effects were highly significant (p?<?0.001) for all alloy–medium combinations. Ordinary least squares regression models demonstrated strong linear relationships between hardness and quench temperature (R²?>?0.90), enabling predictive capability. Metallurgical interpretations attribute aluminium’s sensitivity to precipitation kinetics and solute supersaturation, whereas copper’s low sensitivity reflects its high thermal diffusivity. The findings emphasize the critical importance of precise quench temperature control for aluminium alloys to maximize mechanical performance, while copper alloys allow more flexible processing. Overall, the study provides a robust framework for optimizing industrial quench processes in aluminium and copper components.