Impacts of machining and heat treating practices on residual stresses in alpha-beta titanium alloys

Machining and thermal processing can introduce undesirable residual stresses and distortion in titanium alloy components, and although the distribution and magnitude of these residual stresses is highly relevant for component and process design in the aerospace industry, the relationships between processing variables, processing steps, residual stress signature, and sub-surface microstructures are not well understood. The current study reports on the results of controlled experiments designed to mimic typical machining and thermal processing practices for aerospace alpha-beta Ti alloys. Traditional climb cutting and high-speed peel cutting operations are included in CNC machining experiments, and both stress-relieving and aging heat treatments are considered for thermal processing experiments. Characterization of samples includes strain measurement with optical and strain gauge techniques along with X-Ray Diffraction as well as microstructural characterization using traditional metallographic techniques (optical light microscopy, hardness testing, and electron microscopy). The results of this study provide detailed processing-structure-property relationship information for alpha-beta Ti alloys along with important materials property data that can be used in future ICME studies.