In situ observation of texture evolution during alpha - beta and beta - alpha phase transformations in titanium alloys investigated by neutron diffraction

摘要

Texture changes during recrystallization and the alpha-beta-alpha phase transformation in two titanium alloys were investigated in situ by time-of-flight neutron diffraction by heating in a vacuum furnace to 950 deg C. In commercially pure titanium, a strong texture memory effect is observed. This effect is a direct consequence of an orientation-selective alpha - > beta transformation, favoring new orientations produced during nucleation and grain growth. The beta-alpha transformation favors beta orientations with minimal misorientations, resulting in a strong final alpha texture that emphasizes the grain growth component. In Ti-6Al-4V, the texture memory effect is less pronounced. The high-temperature beta texture is obtained by growth of pre-existing beta nuclei. In a similar way, during cooling, the growth of a domains is controlled by high-temperature alpha orientations inherited from the beta grains with Burgers orientation relation.