Strain Mapping of Al–Mg Alloy with Multi-scale Grain Structure using Digital Image Correlation Method
Al–Mg alloy powder was mechanically milled in liquid N2 (cryomilling) to produce thermally stable powder with nanocrystalline (NC) microstructure for the manufacture of high-strength alloys. A multi-scale microstructure was achieved by blending unmilled coarse-grained (CG) powder with cryomilled powder and subsequently consolidating. The final bulk alloy was comprised of ultra-fine grained (UFG) regions and discrete CG bands. Dynamic observations of tensile deformation of the alloy were recorded using a micro-straining module attached to a light microscope, and the displacements were measured by digital image correlation (DIC). Strain inhomogeneity between UFG regions and ductile CG bands was observed in the micro-strain (strain order of 10−4–10−6) range, and the strain behavior was interpreted in terms of dislocation plasticity. Special emphasis was given to the distinct displacements between adjoining regions during deformation.
KeywordsDigital image correlation Strain mapping Strain localization Cryomilling Ultrafine grains Bimodal grain structures
Financial support was provided by the Army Research Office under contract W911NF-08-2-0028. The authors gratefully acknowledge Prof. Enrique J. Lavernia (University of California, Davis) for providing materials and professional advice, and Prof. Kwang Ho Kim (National Core Research Center For Hybrid Materials Solution, Busan, Korea) for valuable technical discussions. A trial license of the VIC-2D software from the Correlated Solution, Inc. is particularly appreciated.
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