No abstract

In the current investigation, effort has been made to develop the Al-Zinc-Mg alloy by changing weight percentage of Zn (5.1, 5.6 and 6.1) and weight percentage of Mg (2.1, 2.5 and 2.9) through liquid metallurgy process. Developed Al-Zn-Mg alloy is exposed to solutionzing treatment at 450°C for holding period of 3 hrs. followed by ageing at 180C for 3 hrs and then Retrogression Reageing (RRA) at 150C for a holding period of 3, 5 and 7 hrs. Then the modified Al-Zn-Mg cast alloys were cut and machined as per ASTM standard test size specimen. The microstructure shows the irregular grains with different shape and size resulting new grain boundaries. Formation of precipitation in the formed alloy was observed restricting dislocation of grains. The hardness of developed Al-Zn-Mg alloy increased with increase in weight percentage of Mg and Zn for all reageing duration. Further, design of experiments L27 orthogonal array was used to determine the signal to noise ratio, optimization and percentage contribution of each factor. Regression equation show that the experimental values are well within the acceptable range.