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

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 (alpha), fcc (gamma), and hcp (epsilon) 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 (01 (1) over bar0) 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 > {2 (1) over bar(1) over bar2} < 2 (1) over bar(1) over bar3 > and basal (0001)< 2 (1) over bar(1) over bar0 > 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.