Nano- and Micro-mechanical Properties of Ultrafine-Grained Materials Processed by Severe Plastic Deformation Techniques

The processing of metals through the application of severe plastic deformation (SPD) techniques provides the potential for achieving exceptional grain refinement leading to ultrafine-grained (UFG) materials in bulk solids. These materials generally exhibit high strength but very limited ductility at room temperature (RT) leading to the so-called paradox of strength and ductility. The recent development of the novel technique of nanoindentation provides significant feasibility in evaluating the micro-mechanical behavior of UFG materials since the technique provides information on the detailed changes in several mechanical properties during grain refinement through SPD processing. Accordingly, this review examines the available experimental results showing the enhancement in strength and ductility in terms of the micro-mechanical response at RT in a range of metals and alloys after several different SPD processing procedures. A comprehensive tabulation is also presented listing the available data for the strain rate sensitivity, m, in a series of UFG metals processed by SPD.