In situ phase transformation and deformation of iron at high pressure and temperature

Abstract

With a membrane based mechanism to allow for pressure change in a sample in a radial diffraction diamond anvil cell and simultaneous infrared laser heating, it is now possible to investigate texture changes during deformation and phase transformations over a wide range of temperature-pressure conditions. The device is used to study bcc (α), fcc (γ), and hcp (ε) iron. In bcc iron, room temperature compression generates a texture characterized by (100) and (111) poles parallel to the compression direction. During the deformation induced phase transformation to hcp iron, a subset of orientations is favored to transform to the hcp structure first and generate a texture of (011¯0) at high angles to the compression direction. Upon further deformation, the remaining grains transform, resulting in a texture that obeys the Burgers relationship of (110)bcc//(0001)hcp. Contrary to these results for low temperature, at high temperature texture is developed through dominant pyramidal ⟨a+c⟩ {21¯1¯2} ⟨21¯1¯3⟩ and basal (0001)⟨21¯1¯0⟩ slip based on polycrystal plasticity modeling. We also observe that the high temperature fcc phase develops a 110 texture typical for fcc metals deformed in compression.