Straining of a polycrystal of Fe–Pd with martensite structure by uniaxial loading

This paper proposes a method to calculate the uniaxial stress–strain relationship of polycrystalline Fe–Pd, which has a martensite structure produced by cooling. Strain is caused by changes in the fractions of the three Bain corresponding variants which form the martensite structure within each grain. Internal stress and elastic energy are accumulated as straining proceeds and are caused by differences of eigenstrain (transformation strain) between differently oriented grains. The stress and elastic energy are evaluated on the basis of micromechanics. The stress acting on a grain due to surrounding grains is calculated using a mean field method. In this procedure, an averaging method is introduced, by which the mean field of grains having the same tensile direction, but having random lateral directions, are written in a closed form. The averaging method facilitates computations. It is shown that tension and compression differ in the stress–strain relationship.