Effects of Remelting on Variations in Composition, Microstructure, and Hardness Property of Binary Al-Si Alloys

Al-Si binary alloys of 5 to 42 wt.% Si, with a wide range of applications from automotive to space industries, were produced by melting and casting up to ten remelting cycles. This leads to compositional change, showing a variation in Si and the impurity Fe, both of which mutually varied with increasing number of remelting cycle and the selected base alloy composition. The microstructure and hardness of so produced alloys were sensitive to processing conditions, thus leading to quantifiable process–structure–property relationships of power-law type in many cases. The microstructure parameters like grain size and secondary dendrite arm spacing (SDAS) were found to be mutually related and, together, they caused an increase in hardness with microstructure refinement. This obeys Hall–Petch type relationship with its parameters, representing the grain boundary and grain interior strengths, varying interdependently with the processing and composition conditions.