Towards an ICME framework to design post-process treatments for additively manufactured Ti-6Al-4V

Metal additive manufacturing produces net-shape parts and generally introduces local features that need additional heat treatments to tailor the microstructure to meet performance requirements. Because of the local features and defects, the standard heat treatment does not effectively improve the performance as with wrought materials. SwRI has developed a modeling framework that brings insight into the microstructure evolution during the heat treatment and provides an efficient and reliable way to design the manufacturing process.

This presentation will demonstrate an ICME framework to represent the process-structure-properties relations of additively manufactured Ti-6Al-4V. This framework accommodates Python libraries, a materials data curation system, and a hierarchical model to simulate the microstructure evolution during the heat treatment and calculate the stress-strain curve at service temperature. We adopt a heat-transfer model and finite element method to simulate the AM building process. From that, we export the temperature history for Scheil-Gulliver and martensitic transformation models to simulate micro-segregation and estimate the stability of the matrix phase. Another constitutive model, including the classic nucleation, growth, and coarsening of the precipitates, simulates the precipitation in the matrix during the heat treatment. The alloy chemistry is obtained from Thermo-Calc calculations. The transformation kinetics provide the phase fractions and grain sizes for the following models to calculate the stress-strain curve. For this purpose, we implement a physics-based model to estimate the yield strength and a constitutive model to calculate the strain hardening of the Ti-6Al-4V. A Bayesian regression function assists the model calibration and evaluates the model uncertainty. We exercise this framework to design future experiments to improve the model fidelity and minimize the model uncertainty. This presentation will summarize the predicted microstructures and stress-strain curves to compare to the measured values.