Abstract: A new kind of planar defect named non-basal plane stacking faults has been studied by using trace analysis and lattice image techniques.It has been found that they are located in (125)_M plane of martensite lattice.By lattice image observation,the non-basal plane stack- ing faults are argued to be induced by two incomplete basal plane stacking faults and may be the results of rapid quenching.The defects are regarded as anomalous structures of martensite.

Key words: martensite, Cu-Zn-Al alloy, crystal defecis