ABSTRACT
This chapter discusses the occurrence of eutectic and peritectic reactions on the basis of tie-triangles that define the compositions of the reacting phases at various temperatures. The process of peritectic solidification may be illustrated by reference to alloys lying in the region EMNF. These alloys commence solidification by the separation of crystals of a-phase. If the alloy composition lies within one of the single-phase regions AdgCor Bef, then solidification is completed in the manner described for a system showing complete solubility. For alloys lying in the two-phase region defg, the liquid composition reaches curve mn during solidification and with further cooling, the eutectic reaction proceeds until the liquid is consumed. While three phases co-exist, the composition of each phase is restricted to a curve as the temperature changes. An analogous type of critical curve exists for the case of a solid state miscibility gap that closes within a ternary system.
