Quench factor analysis of wrought and cast aluminum alloys

Mechanical property variation across the cross section of heat treatable aluminum alloys is a major concern. To minimize such variation, a proper understanding of kinetic transformations and estimation of mechanical properties is required. The Jominy end quench test has been used successfully to study the effect of quench rate on the final heat treated properties of wrought and cast aluminum alloys. This test produces varying cooling rates along the length of a cylindrical sample cooled with water at one end. Jominy bars of wrought and cast aluminum alloys were solutionized, endquenched, and aged to T6 temper condition after delays of I hour and 120 hours. The hardness values were measured along the length of the Jominy bar. Previous studies have shown that the hardness along the length of the bar follows an A vrami relationship. The present work also measures hardness along the Jominy bar, and the data was used to determine the Avrami parameters (k,n) for various delays and heat treatments of alloys. The accuracy of the Avrami parameters was verified by plotting the calculated Avrami against the hardness data as a function of distance from the quenched end. Mini tensile samples were then taken from specific locations on the Jominy bar. The experimental strength values and their Avrami fit were plotted as a function of distance from the quenched end. Strength values estimated from the Avrami fit were 95% accurate. This study allows prediction of strength at a given quench rate. Finally, cooling curves were simulated at various points along the Jominy bar using FLUENT. Quench factors were calculated along the length of the bar. Using the cooling curves and the calculated quench factors, C-curves were generated for each alloy, and a specific heat treatment applied --Abstract, Page iii