Texture and anisotropy in the mechanical properties of titanium alloys caused by the mechanism of plastic deformation

Abstract

Texture formation during sheet stamping and die forging of α titanium alloys is studied, and the effect of texture and the mechanism of plastic deformation on the strength of internal-pressure spherical vessels is considered. It is shown that, apart from texture, the anisotropy of the strength properties of the α alloys, which is estimated from the difference in the uniaxial-and biaxial-loading strengths, also depends on the chemical composition of the alloy. In the textureless state, the strength of the spherical vessels is higher than the uniaxial strengths of the VT5-1kt, PT3V, and PT3Vkt alloys by 4, 16, and 38%, respectively. This effect is found to be caused by the difference in the relative values of the critical shear stresses for operating slip and twinning systems. The high ductility of the PT3Vkt alloy is related to the fact that it has a ratio of critical shear stresses in the operating slip and twinning systems such that the material is virtually isotropic with respect to tensile loads. This specific feature minimizes the effect of the incompatibility of deformation in grains with different orientations during tension, which is the main cause of the fracture of titanium alloys. The results obtained are used to propose a quantitative criterion to estimate the technological ductility in order to design new titanium alloys.