Effect of Solidification on Microstructure and Mechanical Properties of Aluminium - Silicon Alloys

Microstructures are the key features that provide the backbone for the wear characteristics of all the materials. Structure can be changed by changing the solidification rate. Considering this aspect, two different compositions were prepared, which are Al-Si alloys (5 wt % Si and 12 wt % Si). The specimens were cast by sand casting, chill casting and melt stirred with chilled casting. After that the specimens were prepared for microstructural examination, Brinell hardness test and wear test on pin on disc apparatus was done. In order to understand the distribution of silicon phase, different solidification conditions were used. These influence the development of varieties of structure. It had been observed that the structure, hardness and wear properties were significantly influenced by solidification conditions. Fast cooling, as in chill mould, gives a refined structure which results in finer Si needles. Such a structure provides higher hardness and better wear properties in the alloys. Since Si also acts as a strengthening element, Al-12% Si alloy gives higher hardness.