In Situ Investigation of the Rapid Solidification Behavior of Intermetallic γ-TiAl-Based Alloys Using High-Energy X-Ray Diffraction

Representing an attractive new processing method, additive manufacturing can be used to manufacture parts made of γ-TiAl-based alloys for high-temperature applications. However, in terms of nucleation during rapid solidification and subsequent solid-state phase transformations, the process is not yet fully understood, and research is still going on. This article focuses on a setup to study solidification processes during laser melting via in situ high-energy X-ray diffraction at a synchrotron radiation source. To create conditions similar to those encountered in powder bed-based additive manufacturing processes, such as electron beam melting or selective laser melting, a thin platelet is laser-melted on its upper edge. Phase transitions are measured simultaneously via high-energy X-ray diffraction in transmission geometry. The use of a thin platelet instead of the usual powder bed precludes the unfavorable contribution of solid phases from surrounding powder particles to the diffraction signal. First results of the in situ high-energy X-ray diffraction experiment on a Ti–48Al–2Nb–2Cr (in at%) alloy prove the applicability of the used setup for an accurate tracing of phase transformations upon rapid solidification.