Effect of Dislocation Mechanisms during Extrusion of Nanostructured Aluminum Powder Alloy
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TRODUCTION
NANOSTRUCTURED materials have emerged as a new class of materials with unusual structures. In recent years, creep and superplasticity,[1,2] cold rolling and annealing,[3] and the quantitative understanding of the mechanical behavior[4] of nanostructured materials have been the subject of a number of studies. In particular, experimental studies have focused on grain boundary (GB) diffusion creep, micrograin superplasticity, and the thermally activated propagation of dislocations and their interactions with twin/GBs and dislocation loops, as well as their storage in nanocrystalline grains and quantitative and mechanisms-based constitutive models. Despite the limited availability of data on the mechanical behavior, especially the tensile properties, of nanostructured materials, some generalizations can be made regarding their deformation mechanisms. It is likely that for the larger end of the nanoscale grain sizes, A.M. JORGE, Jr., M.M. PERES, C.S. KIMINAMI, C. BOLFARINI, and W.J. BOTTA, Professors, are with the Department of Materials Engineering, UFSCar - Rod. Washington Luiz, Sa˜o Carlos, Sao Paulo, Brazil 13565-905. Contact e-mail: [email protected] Manuscript submitted November 7, 2008. Article published online October 17, 2009 3322—VOLUME 40A, DECEMBER 2009
approximately 50 to 100 nm, dislocation activity dominates at test temperatures of
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