On the bainitic and martensitic phase transformation behavior and the mechanical properties of low alloy 51CrV4 steel
The role of the austenitization treatment (austenitizing temperature and austenitizing time) on the subsequent phase transformation behavior of low alloy 51CrV4 steel was investigated. The results indicate that the prior austenitization treatment strongly affects both the isothermal bainitic phase transformation kinetics and the onset of the martensitic transformation. In fact, higher martensite start temperatures (
Ms) and longer phase transformation times were present when the austenite grain size increased concomitant with austenitization temperature. In addition, when the supercooled austenite was pre-strained and the subsequent transformation proceeded under a superimposed stress, transformation plasticity strains evolved, whereas higher end values at room temperature were obtained at a lower pre-deformation temperature (T*), which is usually not incorporated in current models. Moreover, tensile tests performed at room temperature following pure bainitic, pure martensitic, or bainitic-martensitic reactions revealed that no linear mixture rule is present for the mixed microstructures. Overall, the current findings demonstrate the necessity of proper incorporation of T* and a non-linear mixture rule for bainitic-martensitic microstructures in low alloy 51CrV4 steel while modeling complex manufacturing processes.