Dynamic observations of deformation in an ultrafine-grained Al–Mg alloy with bimodal grain structure
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The tensile properties and deformation response of an ultrafine-grained (UFG) Al–Mg alloy with bimodal grain structure were investigated using a micro-straining unit and a strain mapping technique. Atomized Al 5083 powder was ball-milled in liquid N2 to obtain a nanocrystalline (NC) structure, then blended with 50 wt.% unmilled coarse-grained (CG) powder, and consolidated to produce a bimodal grain structure. The blended powder was hot vacuum degassed to remove residual contaminants, consolidated by cold isostatic pressing (CIP), and then quasi-isostatic (QI) forged twice. The resultant material consisted of a UFG matrix and CG regions. The dynamic response during tensile deformation was observed using a light microscope, and the surface displacements were mapped and visualized using a digital image correlation (DIC) technique. The DIC results showed inhomogeneous strain between the UFG and CG regions after yielding, and the strain was localized primarily in the CG regions. Strain hardening in the CG regions accompanied the localization and was confirmed by variations in Vickers hardness.
KeywordsDigital Image Correlation Cold Isostatic Pressing Bimodal Microstructure Primary Consolidation Cryomilled Powder
Financial support was provided by the Office of Naval Research under contract N00014-03-C-0163. The authors gratefully acknowledge Prof. Rahul Mitra (Indian Institute of Technology, India) for his professional advice and Correlated Solution, Inc. for providing a trial license of the VIC-2D software.
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