Z.B. Dong

Virtual front tracking cellular automaton modeling of isothermal β to α phase transformation with crystallography preferred orientation of TA15 alloy

A virtual front tracking modified cellular automaton (CA) method is applied to simulate solid phase transformation with a specific crystallographic preferred orientation in a TA15 alloy, to eliminate the dependence of the traditional CA method on space meshing. Simulation results demonstrate the capabilities of the new model in growth anisotropy modeling at large space and time scales, as well as quantitative analysis and description of the precipitated new phase morphology relates to the solute diffusion space by comparison with the diagonal modeling method and rotation of cell sites technique. The isothermal phase transformation kinetics is analysed, which exhibits the desired agreement with the prediction result of the Johnson–Mehl–Avrami analytical equation, thereby a time–temperature-transformation curve is predicted. The crystallography characteristics are consistent with electron backscattered diffraction analysis data. Using the established model, microstructure evolution during the isothermal heat treatment of the TA15 alloy is simulated so that the microstructure heredity with thermal cycling is vividly reflected.

Visco-Elastic-Plastic Constitutive Model for A7N01-T6 Alloy Welding and Analytical Solutions with Finite Element Codes

This paper has established a viscoelasticplastic constitutive model for A7N01T6 alloy welding, which is temperature and deformation history dependent. The model uses elasticmixed hardening plastic and creep equation to describe the strain hardening at low temperatures and strain softening at high temperatures, respectively. Then it is applied for finite element numerical simulation of the welding process. By comparison with the conventional temperature dependent elasticperfectly plastic model, the overall longitudinal residual compressive plastic strain and the maximum deformation of welding sheet are larger. This is because that the plastic strain is mostly produced in high temperature range. Strain softening has great influence on the evolution of plastic strain. The compressive plastic strain during heating is larger than the tensile plastic strain during cooling. Strain hardening effect on welding residual strain and stress is almost negligible. Using the established constitutive model, welding residual stress and strain are in good agreement with the theoretical results.