FINITE-ELEMENT ANALYSIS OF EFFECT OF PRECIPITATE ASPECT RATIO ON ACCOMMODATION ENERGIES DURING SOLID-STATE TRANSFORMATIONS

The initial strain approach of the finite element method (FEM) has bee n applied to evaluate elastic and elasto-plastic accommodation energie s in an ellipsoidal domain as a function of progress of m-P hydrogen t ransformations in the niobium-hydrogen system. In the finite system co nsidered, the progress of transformation from the center of the system outwards and from the surface of the system inwards have been studied . The effect of changing the aspect ratio of a prolate spheroidal prec ipitate on the accommodation energy is addressed. The elastic analysis indicates that the total accommodation energy decreases with increasi ng aspect ratio for all the transformations considered. Moreover, most of the energy is accommodated in the phase in the outer region which surrounds the inner phase. Elasto-plastic finite element analysis of t he hydrogen transformations reveals that plastic deformation of Nb red uces the elastic energy of the system. The elasto-plastic accommodatio n energies at the end of transformation are higher in the case of tran sformations where the final phase is niobium than in the case where th e final phase is niobium hydride. The accommodation energies generally increase with increasing aspect ratio for all the transformation path s considered in the elasto-plastic analysis. (C) 1998 Elsevier Science S.A. All rights reserved.