On the phase transformation and dynamic stress-strain partitioning of ferrous medium-entropy alloy using experimentation and finite element method

Observations based on either side of experiment or modeling often have difficulties in understanding microstructural and mechanical evolutions during deformation, and in application to the macroscopic behavior of materials. In the present study, an integrated experimental-numerical analysis on ferrous medium-entropy alloy (FMEA) was conducted to understand the micromechanical response of the constituent phases in the FMEA at -137 degrees C. The initial face-centered cubic (FCC) single phase microstructure of the FMEA was transformed to body-centered cubic (BCC) martensite during tensile deformation at -137 degrees C, resulting in improved low-temperature mechanical properties. The microstructure evolution due to deformation-induced phase transformation mechanism and strain partitioning behavior was analyzed using ex-situ electron backscatter diffraction. The mechanical responses related to the stress partitioning between constituent phases and deformation-induced transformation rate were measured using in-situ neutron diffraction in combination with the nanoindentation analysis. Three-dimensional microstructure volume element based crystal plasticity models were built based on the experimental observations, and the simulation results were in good agreement with the experimental ones. The concurrent analysis by means of the integrated methodology revealed that the dynamic stress-strain partitioning process between the FCC and BCC martensite enables the superior strain hardening capability and the resulting outstanding low-temperature mechanical properties.