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 subsurface microstructures are not well understood. The current study reports on the preliminary results of 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 solution treating and aging heat treatments are considered for thermal processing experiments. Characterization of samples includes strain measurement using the sin²ψ and cosine α methods with x-ray diffraction as well as microstructural characterization using traditional metallographic techniques. The results of this study show a large tool-path dependence for residual stresses in machined surfaces as well as a significant difference in the residual stress behavior for solution treated and quenched compared to solution treated and aged samples of Ti 6Al-4V alloy.