Titanium as an endogenous grain-refining nucleus

Abstract

Several studies have confirmed the applicability of the inverse growth restriction theory for predicting grain size in titanium alloy systems. However, until now, no work has identified nuclei particles that could be used to refine the β-grain size of titanium alloys during solidification. This work investigated whether titanium powder can be used to nucleate β-grains during solidification. A novel technique was used to introduce titanium powder to a series of titanium alloys, which results in significant grain refinement with an order of magnitude increase in grain density. Electron back-scattered diffraction (EBSD) was used to prove that titanium substrates can epitaxially nucleate titanium during solidification, and although a number of other potential mechanisms were investigated, it was concluded that the titanium particles heterogeneously nucleate β-grains.