Micromechanics, microstrains, and modelling of alpha, alpha-beta, and metastable beta Ti alloys

In spite of six decades of research, the underlying micromechanisms of deformation of titanium alloys, with their diversity of microstructures and single-crystal behaviour, are still not well understood. Synchrotron X-ray and neutron diffraction allow for the evolution of lattice strain, texture, and phase fractions to be studied in real time. Pure Ti has been shown to deform primarily by twinning as opposed to < c+a > slip, resulting in a characteristic lattice strain response and texture evolution. The addition of >2.7%Al has been shown to suppress twinning and promote < c+a > slip. In two-phase alloys, the beta phase usually carries tensile residual lattice strains of up to similar to 40% of the macroscopic yield strain. The stability of the beta phase with respect to both the alpha phase and superelastic phase transformations is a strong function of composition and in turn of the shear modulus C'.