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Examines the surface relief accompanying martensite and bainite in a copper-zinc-aluminum alloy using atomic force microscopy (AFM). Comparison between the transformation mechanism of bainite and martensite; Information on the surface relief effect; Principles of AFM; Description of the three clusters of relief.

The effect of different Nb additions on the mechanical properties and microstructure evolution of grain boundary allotriomorphic ferrite (FGBA) / granular bainite (BG) air cooling bainitic steels was investigated. The results indicate that the tensile strength and yield strength increase by 157 and 97 MPa, respectively with the addition of 0.02wt% Nb. The steel acquires superior strength and toughness with the addition of 0.06wt% Nb. The results of scanning electron microscopy and transmission electron microscopy reveal that the addition of Nb not only refines the size of granular bainite but also increases the volume fraction of granular bainite in FGBA/BG steels. The refinement effect of granular bainite is improved with the increase of Nb content. [ABSTRACT FROM AUTHOR]

A transmission electron microscopy (TEM) study was made of the interphase boundary structure between the matrix and α1 plates formed at 250 °C, 300 °C, and 350 °C in three Cu-Zn-Al alloys. The experiments showed that the α1 plates formed at each temperature studied in all of the alloys are initially free of stacking faults. This observation, confirming the results of previous investigations, shows that these plates cannot have formed by a shear mechanism. Ledges were shown to exist on the broad faces and/or at the growth edges of the α1 plates. Indirect evidence implies that the ledges are mobile and that they can migrate along different directions on the broad faces. [ABSTRACT FROM AUTHOR]