INHOMOGENEITY OF PHASE-TRANSFORMATIONS BETA-]OMEGA AND BETA-]ALPHA INTHE QUENCHED COLD-ROLLED ALLOY ZR-20-PERCENT-NB

The inhomogeneous character of phase transformations in the quenched c old-rolled alloy Zr-20%Nb was investigated using new X-ray diffractome tric procedures based on a position sensitive detector. It was shown t hat the distribution of strain hardening in beta-grains with different orientations controls the development of phase transformation beta -- > alpha and beta --> omega in the rolled alloy. Derivative phases inhe rit the substructure inhomogenity of the beta-phase, i.e. their grains are most dispersive and/or have the most distorted crystalline lattic e in texture minima, where both phase transformations develop primaril y. To explain the obtained X-ray texture data a mechanism was suggeste d involving local formation of quasi-amorphous boundary interlayers by cold rolling and their crystallization by annealing.