X-ray diffraction for phase identification in Ti-based alloys: benefits and limitations

Abstract

X-ray diffraction (XRD) is routinely used to characterise Ti alloys, as it provides insight on structure-related aspects. However, there are no dedicated reports on its accuracy are available. To fill this gap, this work aims at examining the benefits and limitations of XRD analysis for phase identification in Ti-based alloys. It is worth mentioning that this study analyses both standard and experimental Ti alloys but the scope is primarily on alloys slow cooled from high temperature, thus characterised by equilibrium microstructures. To be comprehensive, this study considers the all spectrum of Ti alloys, ranging from alpha to beta Ti alloys. It is found that successful identification and quantification of the phases is achieved in the majority of the different type of Ti-based alloys. However, in some instances like for near-alpha alloys, the output of XRD analysis needs to be complemented with other characterisation techniques such as microscopy to be able to fully characterise the material. The correlation between the results of XRD analysis and the molybdenum equivalent parameter (MoE), which is widely used to design Ti alloys, was also investigated using structural-analytical models. The parallel model is found to be the best to estimate the amount of β-Ti phase as a function of the MoE parameter.