SELF-ACCOMMODATION MORPHOLOGY OF MARTENSITE VARIANTS IN ZR-2.5WT-PERCENT-NB ALLOY

The role of self accommodation of the different martensite variants in controlling the morphologies of the Zr-2.5wt%Nb alloy martensite has been examined. Three distinct types of grouping of martensite variants have been found to be predominantly present. Crystallographic descrip tions of these groups have been provided and the degrees of self accom modation for these have been estimated and compared with those corresp onding to other possible variant groupings around the symmetry axes of the parent phase. The frequently observed 3-variant group, which show s an ''indentation mark'' morphology when viewed along [111]beta direc tions in the transmission electron microscope, has been seen to have t he highest degree of self accommodation amongst the cases considered. Based on the observations made, a growth sequence leading to the forma tion of the final martensitic structure has been proposed.