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The microstructures of y-TiAl
alloys. alloyed with small amounts of silicon are studied and the nature and distribution of different phases observed in the as cast and heat treated conditions are investigated. The high temperature heat treatments of the alloys resulted in a range of transformation mechanisms producing microstructures such as lamellar (a2+Y) . acicular and massive y obtained from a phase. Different modes of the a phase
decomposition are discussed in terms of alloy composition and cooling rate. The addition of silicon is found to have an important role in this regard.