Determination of flow stress behavior of materials is a critical aspect of understanding and predicting behavior of materials during manufacturing and use. However, accurately capturing the flow stress behavior of a material at different strain rates and temperatures can be challenging. Non-uniform deformation and thermal gradients within the test sample make it difficult to match test results directly to constitutive equations that describe the material behavior. In this study, we have tested AISI 9310 steel using a Gleeble 3500 physical simulator and Digital Image Correlation system to capture transient mechanical properties at elevated temperatures (300°C – 600°C) while controlling strain rate (0.01 s-1 to 0.1 s-1). The data presented here illustrate the benefit of capturing non-uniform plastic strain of the test specimens along the sample length, and we characterize the differences between different test modes and the impact of the resulting data that describe the flow stress behavior.

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Vacuum carburizing of 9310 gear steel followed by austenitizing, oil quench, cryogenic treatment, and tempering is known to impact residual stress state of the steel. Residual stress magnitude and depth distribution can have adverse effects on part distortion during intermediary and finish machining steps. The present research provides residual stress measurement, microstructural, and mechanical property data for samples taken along a specific heat treat sequence. Test rings of AISI 9310 steel are subjected to a representative gear manufacturing sequence that includes normalizing, rough machining, vacuum carburizing to 0.03”, austenitizing, quench, cryo-treatment, temper, and finish machining. Characterization of a test ring and a metallurgical sample after each manufacturing step allows tracking of residual stress and microstructural changes along the sequence. The results presented here are particularly interesting because the highest compressive residual stresses appear after removal of copper masking, not after quench as expected. Data can be used for future ICME models of the heat treat and subsequent machining steps. Analytical methods include X-Ray Diffraction, optical and electron microscopies, mechanical testing, and hardness testing.

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 stress-relieving and aging heat treatments are considered for thermal processing experiments. Characterization of samples includes strain measurement using the sin2ψ method with X-Ray Diffraction as well as microstructural characterization using traditional metallographic techniques. The results of this study point to potential areas for improving tool approach in machining practices for α-β Ti alloys.