Effect of shear strain on the α–ε phase transition of iron: a new approach in the rotational diamond anvil cell

Abstract

The effect of shear strain on the ironα–ε phase transformation has been studied using a rotational diamond anvil cell (RDAC). Theinitial transition is observed to take place at the reduced pressure of 10.8 GPa underpressure and shear operation. Complete phase transformation was observed at 15.4 GPa.The rotation of an anvil causes limited pressure elevation and makes the pressuredistribution symmetric in the sample chamber before the phase transition. However,it causes a significant pressure increase at the centre of the sample and bringsabout a large pressure gradient during the phase transformation. The resistanceto the phase interface motion is enhanced due to strain hardening during thepressure and shear operations on iron and this further increases the transitionpressure. The work of macroscopic shear stress and the work of the pressure andshear stress at the defect tips account for the pressure reduction of the iron phasetransition.