Structure of directionally solidified two phase ternary alloys

Simple theories developed in a series of recent papers, describing solid/liquid interface stability and solute redistribution in three phase ternary alloys are summarized and extended to apply to ternary alloys that are two phase on equilibrium solidification. Calculated results compare well with experiments on alloys from the Al-rich corner of the Al-Cu-Ni ternary phase diagram. These alloys represent the type currently under development for gas turbine applications. At sufficiently high values ofG/R (thermal gradient divided by growth rate) the alloys grow with a fully plane front. At moderate values ofG/r they exhibit a unique structure of single phase cells and two phase intercellular root material which grows with a “plane front”. Further decreases inG/R produce more typical ternary cellular structures with regions of one, two and three phases.