Electron Diffraction Study of Stacking Disorder in the Plastically Deformed Martensite of Cu-Al Alloy

Shifts of the electron diffraction spots of the plastically deformed β' martensite of Cu-11.04wt.% Al alloy have been examined using the selected-area diffraction method of an electron microscope. The analysis of these shifts shows the existence of various states of stacking disorder corresponding to α=0∼0.6 where α is a stacking fault parameter representing cubic type stackings. The states of staking disorder corresponding to α=0.6∼1.0 are not found; instead there exist structures which are expressed as (7\bar1), (8\bar1) 3 , (10\bar1) and (11\bar1) 3 by Zhdanov notation. These structures are considered to be energetically more favorable than the f.c.c. structure for the alloy used.