Study of as-cast structure formation in Titanium alloy

Titanium alloys are an important class of materials for light-weight, high strength and high temperature applications. They are widely use in the aerospace sector. Melting and solidification of Titanium is very common in industrial practice, either during the alloy production or during casting of components. Despite this, the formation of as-cast structure in Ti-Alloys has received very little attention so far. This can be attributed to the difficulty of studying solidification behaviour of these alloys, which are very reactive, with high melting temperatures and undergo a solid-state transformation upon cooling which makes the as-cast structure very difficult to observe.
In this study we present an attempt to overcome the aforementioned challenges. Samples of Ti-1023 and Ti-64 have been processed by plasma-arc-melting (PAM) in a laboratory size copper crucible, involving melting and solidification. The observed microstructure shows break-up of planar solidification fronts, and columnar to equiaxed transitions during solidification. Dendrites can be clearly observed from microsegregation patterns.