Influence of subgrain orientation on martensitic transformation in beta(1)-Cu-Zn-Al-single crystals

In beta(1)-Cu-Zn-Al single crystals the course of cyclic martensititic tran sformation 'beta(1) parent phase <-> gamma'(1) martensite' induced by tensi le stress were studied with use of X-ray topography, light microscopy and e tch pits. Two groups of single crystals were studied. The first one (OR) co ntained single crystals of subgrain boundaries parallel to the direction of elongation [001], the second one (RA) consisted of single crystals of rand om subgrain boundaries orientations. Single crystals from the RA group crac ked after about 300 cycles of martensitic transformation; single crystals f rom the OR group did not crack even after 1200 cycles. In OR single crystal s changes of dislocation density inside the subgrains caused by cycling occ urred much more slowly than in the RA single crystals. This has been relate d to the dislocation movement from inside the subgrains to their boundaries . Published by Elsevier Science S.A.