CHARACTERIZATION OF AL-8090 SUPERPLASTIC MATERIALS USING ORIENTATION IMAGING MICROSCOPY

A fundamental understanding of the deformation mechanisms of superplas ticity requires a detailed characterization of the microstructure. For certain studies, optical microscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques used in conve ntional mode may be inadequate for detailed analysis. This paper prese nts the use of a newly developed technique, 'orientation imaging micro scopy' (OIM) in characterizing the microstructure of an Al-8090 alloy deformed in uniaxial tension to strains of 15, 70 and 660% at 520 degr ees C and 5 x 10(-4) s(-1) strain rate. In OIM the microstructure is c onstructed from the measured crystal orientations obtained from points on the specimen surface distributed in a hexagonal grid, Neighboring measurements with a misorientation greater than a specified value. ome ga, misorientation angle criteria (designated by the researcher) are d eemed to define the location uf grain boundaries. These boundary lines can be interpreted as high angle grain boundaries or subgrain boundar ies depending on the value of omega. The implications of the analyses on superplastic deformation are discussed. (C) 1998 Elsevier Science.