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Development of Surface Mechanical Attrition Treatment (SMAT) and Electrodeposition Process for Generating Nanostructured Materials and Study of Their Tensile Properties

Posted on:2011-11-01Degree:Ph.DType:Thesis
University:Hong Kong Polytechnic University (Hong Kong)Candidate:Chan, Hoi LamFull Text:PDF
GTID:2441390002455572Subject:Engineering
Abstract/Summary:
This work systematically investigates two of the most promising synthesis methods for producing nanostructured (NS) materials: surface mechanical attrition treatment (SMAT) and the electrodeposition (ED) process, and obtains the proper conditions for fabricating NS materials in bulk form and studies the properties of these materials.;SMAT is one of the recently developed processes to form nano-crystallized surface layer and refine grains in the subsurface layers, by actuating a number of spherical projectiles to impact the sample surface. In this work, the detailed measurement of ball impinging velocity is presented, and the resulted strain-rate and strains are theoretically modeled. Consequently the relation between plastic strain history and the observed microstructures is established. The SMAT process with different numbers of balls is explored to manifest that an optimum number of balls exists for the highest efficiency.;ED process is widely used in producing NS materials these days. In this work, the relationships among non-metallic substrates, current type, current densities, microstructure and crystallographic textures, and mechanical properties is presented in order to demonstrate the influences of the deposition parameters in obtaining nano-grains and nano-twins microstructures. This work also examines the availability of obtaining bulk NS materials with desirable ductility in production-scale conditions through understanding these relationships.;In the last part of the study, the effect of SMAT on the electrodeposits is studied. Tensile properties, microstructures and textures of the SMATed electrodeposits have been examined. The results demonstrate that the NS matrix obtained by the ED process with sufficient thickness retains desirable ductility after employing SMAT technology, and the SMAT process further enhances the strength of the electrodeposits.
Keywords/Search Tags:SMAT, Process, Materials, Surface, Mechanical, Work
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