Microstructure and Textures in Rolled and Recrystallized Ni 3 Al + B
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MICROSTRUCTURE AND TEXTURES IN ROLLED AND RECRYSTALLIZED Ni3AI + B
JOACHIM BALL AND G. GO1TSTEIN Institut fiir Metalikunde und Metaliphysik, RWTH Aachen Kopernikusstr. 14, 5100 Aachen, FRG
ABSTRACT The deformation and recrystallization structure as well as the evolution of crystallographic textures of heavily deformed, partially and fully recrystallized Ni 3AI, ductilized with minor additions of boron, were investigated. The macroscopic orientation distribution was determined by X-ray polefigure measurements and subsequent computation of the orientation distribution function (ODF). Convergent electron beam diffraction (CEBD) was employed to obtain information on the orientation topography and the orientation relationship of volume fractions adjacent to deformation inhomogeneities. Single grain orientation measurements by electron back scattering patterns (EBSP) were carried out to study the orientation distribution of new grains in the recrystallized microstructure. From this data the microtexture and the misorientation distribution function were calculated and the grain boundary character distribution was analysed. The results are discussed with regard to the mechanisms which govern the evolution of the conspicuously inhomogeneous deformation microstructure and deformation textures. A model for the interpretation of the observed microstructure and texture evolution is proposed. INTRODUCTION The current study is concerned with the microstructural evolution and texture development of ductilized Ni3Al during cold rolling at low homologous temperatures and during recrystallization. The investigation is aimed at a deeper understanding of the mechanisms which govern the evolution of the rather complex deformation microstructure and resulting weak deformation texture as well as the occurrence of recrystallization in ordered intermetallics. For this purpose systematic studies have been carried out employing optical microscopy, TEM investigations (CBED), texture determination by X-ray pole-figure measurements with ODF computation and individual grain orientation measurements by EBSP in a SEM. EXPERIMENTAL PROCEDURE A nickel aluminide with the composition NiýAi,+0.24at% B (IC15 according to Oak Ridge National Laboratory terminology) was investigated. A detailed description of the specimen preparation and thermomechanical heat treatment is given elsewhere [1]. Macrotexture measurements for various rolling reductions at room temperature as well as for progressive stages of recrystallization were performed. Metallographic specimens were prepared from deformed, partially and fully recrystallized material. All optical and electron microscopy observations were made on the transverse plane of the rolling specimen. The local orientation distribution in deformed and partially recrystallized Ni3 AI was determined in the TEM by means of CBED. For microtexture measurements of recrystallized specimens EBSP in a SEM was employed.
Mat. Res. Soc. Symp. Proc. Vol. 288. @1993 Materials Research Society
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RESULTS During cold rolling t
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