Length Scale Effects on Deformation and Failure Mechanisms of Ultra-Fine Grained Aluminum
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Length Scale Effects on Deformation and Failure Mechanisms of Ultra-Fine Grained Aluminum K. Hattar1, J. H. Han2, D. M. Follstaedt3, S. J. Hearne3, T. A. Saif2, I. M. Robertson1 1 Materials Science and Engineering, University of Illinois, 1304 W. Green St. Urbana, IL 61801 USA 2 Mechanical and Industrial Engineering, University of Illinois, 1206 W. Green St. Urbana, IL 61801 USA 3 Sandia National Laboratories P. O. Box 5800, MS 1056 Albuquerque, NM 87185
ABSTRACT The deformation and failure processes in ultra-fine grained aluminum over different length scales have been probed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) in combination with a micromechanical in situ straining device. This novel straining device affords the opportunity to correlate directly the macroscopic mechanical properties with the microscopic deformation and failure mechanisms. Through use of this device it has been shown that increased film thickness results in a transition between limited plasticity and intergranular fracture to global plasticity and shear failure for deposited aluminum samples of similar grain size but different thickness. INTRODUCTION The mechanical properties of nanograined and ultra-fine grained metals exhibit a higher yield and fracture strength, lower elongation and toughness, higher strain rate sensitivity, higher strain rate sensitivity index, lower (
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