STATISTICAL OPTIMIZATION OF THE MECHANICAL PROPERTIES OF HEAT TREATED ALUMINUM BRONZE (CU-10%AL) USING RESPONSE SURFACE METHODOLOGY.

Abstract

Mathematical models have been derived for the prediction of the mechanical properties (Ultimate tensile strength (UTS), Yield Strength and %Elongation) of heat treated Aluminum bronze alloy. The aim of the research is to improve on the mechanical properties of the alloy using ageing heat treatment. The selected heat treatments were Solutionizing, Quenching and Ageing. Response Surface Methodology (RSM) was employed to investigate the influence of the process variables (ageing temperature and soaking time) on the mechanical properties. The two level-2 factor Central Composite Design (CCD) used in this study required 13 experiments. The cast specimens were solutionized at 900℃ for 1hr, quenched in water and then aged at temperatures of 109℃, 150℃, 250℃, 350℃ and 391℃, soaked for 5min, 25min, 73min, 120min and 140min respectively, according to the experimental design. The best combination of mechanical properties was achieved at ageing temperature of 350℃ and soaking time of 120mins which gave 565MPa for UTS, 480MPa for Yield Strength and 17.8%E. A model following a second order Polynomial which includes interaction terms was used to calculate the predicted responses.