Rapid quenching of semisolid Ti-Cu alloys: Insights into globular microstructure formation and coarsening

Abstract

Thixoforming is a typical semisolid processing route for the production of affordable near-net shape metallic components. In this study, Ti-Cu alloys specifically designed for thixoforming were evaluated to determine their microstructural evolution in the semisolid state. Ti-(25, 27, 29)Cu (wt.%) alloys were prepared by voltaic arc melting, homogenized, and then hot worked prior to isothermal heat treatment at 1035 °C. Rapid quenching allowed for the investigation of “frozen” semisolid microstructures. The results indicated the formation of fine grained globular microstructures in all the alloys under study. This was attributed to the deformation process, which was able to break up the dendrites resulting from solidification. The liquid fraction increased with Cu content and its values were consistent with those predicted under equilibrium, although evidence of some nonequilibrium liquid was still present during the time period of analysis. Lastly, coarsening rate constants (K) exhibited low values, indicating stable semisolid microstructures.