Investigating the Effect of Rapid Heating on Microstructure and Tensile Properties of Phosphorus Modified Alloy Al-Si-Cu-Mg

The effect of chemical modification of a hyper eutectic Al-Si alloy using phosphorus ‎on the efficiency of solutionizing heat treatment in modifying the primary Si has ‎been studied in the current paper. In order to enhance the effect of heat treatment in ‎the modification of the primary Si, the cast specimens modified by phosphorous were ‎solutionized and then microstructurally and mechanically compared with the heat treated ‎unmodified ones. To characterize the microstructure and mechanical properties, ‏optical microscopy, scanning electron microscopy (SEM) and tensile test were ‎performed. The results revealed that chemical modification reduces the primary ‎silicon particles size without any change in Si particles shapes‏. Nevertheless, due to ‎increasing the surface to volume ratio of the particles, the influence of the post heat ‎treatment on the shape of the primary silicon particles was enhanced. Based on the ‎results, the primary silicon particles’ nodularity in the phosphorus modified ‎specimens increased from 32 to 47 percent upon heat treatment process. In addition, ‎‎32 and 33 percent increments in the ultimate tensile strength and ductility were ‎obtained, respectively, after applying the post heat treatment to the P-modified ‎specimens compared to the as cast ones.