Abstract
The present study was undertaken to investigate the effect of a number of metallurgical parameters on the tensile properties and quality indices of Al-9%Si cast alloys, i.e., 354 and 359, containing 1.8%Cu-0.5%Mg and 0.5%Mg, respectively. The variables investigated were the strontium content, solidification rate and heat treatment conditions. Quality charts were used as a tool to recommend the optimum conditions to be applied to the 354 and 359-type castings. An increase in the solution heat treatment time enhances the tensile properties and the quality index values of the 354 and the 359 alloys. Twelve h was the time judged most suitable for optimum solution heat treatment of these alloys. The solution heat treatment time required to attain specific tensile properties in the unmodified 354 and 359 alloys may be shortened by modifying these alloys with strontium. The effects of Sr-addition on the response of the 354 and 359 alloys to solutionizing treatment diminish upon increasing the solution heat treatment time as, after a certain length of time, both modified and unmodified alloys display almost the same properties for the subsequent solutionizing time. A rapid solidification rate enhances the tensile properties of both 354- and the 359-type casting alloys due to the refinement of the SDAS; modification of eutectic silicon particles; and reduced size and levels of porosity.