Imperfect dislocations at non-basal plane defects in 18R and 2H martensites: transmission electron microscopy studies

A detailed study of the non-basal plane (NBP) faults in 18R and 2H martensi tes in CuZn-Al alloys has been performed, using transmission electron micro scopy and high-resolution transmission electron microscopy. Four types of N BP fault are possible in the 18R martensite. This set reduces to F-o and F- x after convenient atomic relaxations, producing six types of imperfect dis location depending on the type of basal plane fault finishing at the NBP fa ult. The Burgers vectors of all these dislocations have been determined fro m the analysis of the images. On the ether hand, the displacement vectors d ue to the atomic relaxation along the F-1 and F-2-type faults in the 2H str ucture have been carefully determined from the analysis of the dislocations formed at the intersection of the NBP and the basal plane stacking faults. All the relaxations are consistent with the conservation of the volume per atom at the NBP faults. Both NBP faults reduce themselves to the same kind of fault with different dislocations at their ends.