MORPHOLOGY AND STRUCTURE OF TRANSFORMATION PRODUCTS FORMED AT INTERMEDIATE TEMPERATURE IN A Cu-Zn-A1 ALLOY"
(Shanghai Jiao Tong University, Shanghai 200030, China)
Abstract: A TTT diagram for the precipitation formed at some intermediate temperatures through cooling from high temperature parent phase in a Cu-27.27Zn-3.73A1 alloy is established by means of dilatometric measurement. The morphology and structure of transformation products formed at some intermediate temperatures isothermally through cooling from high temperature parent phase and up-quenching from DO3 parent phase are studied by metallographic, X-ray and electron microscopy analyses. Three regions in the two separate C curves are obtained according to different morphology of precipitate: rod-like α, plate-like bainite and α rods, and bainite plates. Prolonged aging makes bainite plate change gradually into αwhose lattice parameters are no different from that of αformed equilibriumly from parent phase. The structure is almost orthorhombic long period structure for bainites formed from B2 and DO3 parent phase, but monoclinic for martensite from DO3. They correspond to the overlapping and separating of (1 2 10) and (2 0 10) diffraction peaks respectively, showing the lower degree of ordering in bainite
Key words: Cu-Zn-A1 alloy transformation at intermediate temperature morphology and structure