Selection of lattice invariant shear in dilute Zr-Nb alloy for bcc-hcp martensitic transformation

Abstract

The morphology and substructure of martensite is considered to arise from the lattice invariant shear (LIS) associated with the transformation and this may be slip, twinning or both. Out of the several possible slip shears and twin modes only a few satisfy invariant plane strain criteria of the phenomenological theory of martensite (PTMC). On the basis of crystallographic and energetic criteria, a simple model has been proposed for determining the factors which influence the selection of the preferred LIS mode. In the present work, it is found that for β → α ′ martensitic transformation in Zr-2.5 wt%Nb alloy, the preferred slip system is {1^-101}_{α ′}<21^-1^-3>_{α ′} and the preferred twin system is {1^-101}_{α ′}<415^-3>_{α ′}.