Multiscale Analysis of the Microstructure and Stress Evolution in Cold Work Die Steel during Deep Cryogenic Treatment

Through a combination of 3D representative volume element (RVE) and the metallo-thermo-mechanical coupling finite element (FE) analysis, a multiscale model was established to explore the localized characteristics of microstructure and stress evolution during deep cryogenic treatment (DCT). The results suggest that after cooling to near -160 °C, the largest intensity of martensite is formed, but the retained austenite cannot be eliminated completely until the end of DCT. The driving force for the precipitation of fine and uniform carbides during DCT is provided by the competition between the thermal and phase transformation stresses. Compared with the thermal stress, the phase transformation stress during DCT plays a more significant role. At the interface between retained austenite and martensite, a reduction of around 15.5% retained austenite even induces an obvious increase in the phase transformation stress about 1100 MPa. During DCT, the maximum effective stress in RVE even exceeds 1000 MPa, which may provide a required driving force for the precipitation of fine and homogeneously distributed carbide particles during DCT.