Electron Microscopic Study on the Fine Structure in Metastable β<SUB>1</SUB> Crystal of Cu-40 wt% Zn alloy

Abstract

Very fine contrasts have often been observed in transmission electron microscopic images of quenched β-brass crystal. The contrasts are related to the presence of very fine transformation products in metastable matrix crystal. The crystal structure of the product has been invertigated in this survey by analysing electron diffraction patterns containing additional diffraction spots produced by the products. The mechanism of the transformation was also discussed.The crystal structure obtained is an orthorhombic structure with A=(2a⁄3)[1\bar12]β1, B=(a⁄2)[1\bar1\bar1]β1, C=a[110]β1, which is also considered as a deformed hcp structure. It is supposed that the (110)[\bar110]β1 shears play an important role in producing the fine product, that is, the transformation possesses a martensitic nature. The fine products are thought as embryos of close-packed structure, such as martensite or bainite, not having enough energy to grow in large and perfect close-packed crystals.