Influence of High Hydrostatic Pressure on the α-σ Transformation of an Fe-Cr Alloy

Abstract

Investigations of the α-σ isothermal transformation of an Fe-Cr alloy containing about 45 at%Cr were carried out at various hydrostatic pressures up to 900 MPa, and the rate of the transformation and the behaviour of crack formation in σ-phase were examined. The rate of the transformation was accelerated under high hydrostatic pressures and was suggested not to be controlled by diffusion. The time necessary to obtain a given amount of the σ phase at 900 MPa was 1/2 to 1/1.5 times shorter than that at atmospheric pressure. The formation of the crack in the σ phase was inclined to be suppressed under high hydrostatic pressures. A good number of specimens made of the σ phase having few cracks were obtained at 900 MPa. Elastic constants measured with such σ phase specimens are as follows: Young’s modulus=209 GPa, shear modulus=79.8 GPa, bulk modulus=186 GPa and Poisson’s ratio=0.31.