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Characterization of Zinalco Alloy Superplastically Deformed Using Orientation Imaging Microscopy Ramos A. Mitsuo 1, Martínez F. Elizabeth 2, Negrete S. Jesús 1, Torres-Villaseñor G. 3 1

Instituto de Metalurgia-U.A.S.L.P. Sierra Leona 550, Lomas 2a. Sección, 78210, S.L.P. Mex.

2

Facultad de Ingeniería-U.A.S.L.P. Dr. Manuel Nava 8, Zona Universitaria, 78290, S.L.P. Mex.

3

Instituto de Investigaciones en Materiales-UNAM, C.U., Apdo. Postal 70-360, 04519 Mex. DF.

ABSTRACT Zinalco alloy (Zn-21mass%Al-2mass%Cu) specimens were deformed superplastically with a strain rate (  ) of 1x10-3s-1 at homologous temperature (TH) of 0.68 (513 K). It was observed neck formation that indicate nonhomegeneus deformation. Grain size and grain boundaries misorientation changes, due superplastic deformation, were characterized by Orientation Imagining Microscopy (OIM) technique. It was studied three regions in deformed specimens and the results were compared with the results for a specimen without deformation. Average grain size of 1 mm was observed in non-deformed specimen and a fraction of 82% for grain boundary misorientation angles with a grain boundaries angles between 15º and 55º was found. For deformed specimen, the fraction of angles between 15º and 55º was decreced to average value of 75% and fractions of low angle (55º) misorientations were 10% and 15% respectively. The grain size and high fraction of grain boundary misorientation angles between 15º and 55º observed in the alloy without deformation, are favorable for grain rotation and grain boundary sliding (GBS) procces. The changes observed in the fraction of favorable grain boundary angles during superplastic deformation, shown that the superplastic capacity of Zinalco was reduced with the deformation. INTRODUCTION The study of the microstructure of polycrystalline materials involves the analysis of parameters such as shape grain, size grain and grain misorientation. It is possible make these analysis through the reconstruction of the microstructure using Kikuchi patterns obtained with the Electron Backscatter Diffraction (EBSD) technique [1-2]. In this technique an electron beam generated inside a Scanning Electron Microscope (SEM), impact on the sample with an angle of 70° and backscattered electrons produced by this interaction are intercepted by a phosphorescent screen [1-4]. The diffraction pattern is a function of the crystalline phase and crystalline orientation. Using a recent technique called Orientation Imaging Microscopy (OIM) [3-4], it is possible to collect and index every pattern to determine which phase it belongs to. With the OIM-EBSD technique it is possible to analyze features such as misorientation between grains, which should be described in terms of the distribution probability of misorientation angle between boundaries of adjacent grains [5]. This misorientation angle is the lowest angle among all equivalent crystallographic rotations that makes matching two crystal

lattices [1, 5-7]. A misorientation between the grains with an angle equal to or