Titanium sponge as a source of native nuclei in titanium alloys

Abstract

Equiaxed β-grain morphologies have been observed in a wide array of Ti alloys produced by numerous solidification-based processes and, in terms of conventional solidification theory, are believed to be a consequence of heterogeneous nucleation upon native nucleant particles during solidification. In contrast, the source of these heterogeneous nuclei has yet to be established or explored in detail. In this work, titanium sponge was investigated as a possible common-denominator source of these nuclei. It was found that the native nuclei populations in titanium alloys may consist of transient interstitial-based compounds and fragments of titanium. A residual contaminant identified on the commercial titanium sponge pieces (sodium chloride), was also found to be effective at promoting smaller as-cast prior-β grain sizes.