Effect of Alloying Element on A1-12.6%Si Eutectic Alloys

Abstract

Al-Si alloys are in demand for several structural devices because of their high strength to weight ratio. The enhancements in properties are further observed when suitably alloyed with the different elements. Al-Si alloy find their application mostly in automobile engineering. Alloys of eutectic composition are used as piston alloys as Si exhibit good wear properties. Si in the matrix nucleates as needle structure when solidified. These needle structures when modified exhibit very good thermal and wear properties. In the present work attempt has been made to modify Al-Si eutectic microstructure by alloying it with certain amount of immiscible elements. These have been tried singly and as well as in combinations. It has been observed that all elements have tendency to modify the structure by adding as a barrier center for the growth of Si needles. However, in certain cases this growth is not up to the mark. The idea behind this work was to see the effect of addition of immiscible alloys for the refinement of microstructure. The theory of homogenous nucleation proposed by Volmer and Creber (1925) state the nucleation phenomena is governed by surface and volume free energy. However, this theory could not be satisfied for alloy systems. In this entire work it was observed that the refinement of Si needles could be observed for all composition studied for Bi, Pb, Ca, Cd and Sn.