Research Projects

Displaced phase transformations (DPTs) are crucial for the properties of shape memory alloys and improved yield strength in various materials. These transformations involve the transformation of a parent phase into a product phase with different crystal structures. Plastic strains-induced DPTs are common in industrially important materials like iron, steels, Ti, Zr, Hf, Nb, Mg, and some of their alloys. The yield strength of these materials is much lower than the stresses required for stress-induced transformations. The stress concentration within the plastic strain localization near grain boundaries, triple junctions, isolated shear bands, and their intersecting regions promotes phase transformations. The proposal aims to develop large strains-based thermodynamically consistent theories to study strains-induced DPTs at two different length scales, i.e., nano and microscale. A nanoscale phase-field model will study the nucleation and growth of phases from dislocations and their pile-ups, while a microscale strain-gradient plasticity model will be developed to study the effects of dislocations separated by distance ∼ 10 nm. Large-scale simulations in polycrystals will require high-performance computers. In-situ high-pressure torsion tests will be conducted on commercially available high-purity titanium and zirconium to validate the model and simulation results.