Two-phase (α/β)-brass bicrystals produced by a solid-solid diffusion method: I. Morphology and crystallographic relationships between the α-and β-phases

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Abstract
The morphology of two-phase (α/β)-brass couples produced by a solid-solid diffusion method has been investigated. Macroscopic units made of a parent single crystal of the α-phase and a transformed β-phase (two-phase α/β-bierystals) can be obtained which are suitable for mechanical testing. Interphase boundaries of the bicrystala have been found to be essentially planar and, when the concentration change near the interface is less than about 6% in the α-phase, no special structural defects have been detected in the α-and transformed β-phases by means of an etch-pitting technique. Crystallographic orientation relations between the phases were studied in detail, employing mainly (111)-surface-oriented α-brass crystals and transformed β-phases using the usual back-reflection Laue method. A theoretical relation predicted from Bollmann's O-lattice method by Perio, Bacmann, Suéry and Eberhardt (1977), which lies between the Kurdjumov-Sachs (K-S), the Nishiyama-Wassermann (N-W) and the inverted Nishiyama-Wassermann (I-N-W) relations, has been established to occur preferentially followed, with lower probability, by the N-W and the K-S relations. Furthermore, from the observed relationships for the (011)α-and (001)α-orientated couples and previously reported results by other authors, it is argued that preferential relations may be influenced by the interface orientations of the parent α-brass crystals so as to attain well fitting interfaces. Preliminary observations of the characteristic interphase boundary ledges (IBL), which sometimes appear in couples having interface planes of higher indices, are presented. It is strongly suggested that the facets of the IBL are parallel to the {110}β planes.