Talk given by

Prof. Satyam Suwas

Department of Materials Engineering

Indian Institute of Science

Bangalore, India

Abstract:

It is well known that the mechanisms associated with the evolution of microstructure and crystallographic texture in face centred cubic (FCC) materials is dependent on stacking fault energy (SFE) and grain size, independently. Severe plastic deformation processes that lead to grain refinement respond differently to FCC materials with different stacking fault energies and initial grain sizes. In this work, the combined role of stacking fault energy (high to low) and initial grain size (microcrystalline and nanocrystalline) has been explored, especially pertaining to grain refinement and texture formed in FCC materials after high pressure torsion, a well known severe plastic deformation technique. The results indicate that the deformation mechanism involves twinning and grain boundary sliding for the low SFE and nanocrystalline materials, in addition to dislocation slip which is predominant for high SFE and micro-crystalline materials. Textures are generally weak; however, the trends in texture evolution corroborate the results of microstructural investigations. In the micro-crystalline materials, grain refinement is the dominant process. However, a saturation grain size is observed for each composition after a certain deformation level. On the other hand, deformation induced grain growth has been observed in the case of nanocrystalline materials. A comprehensive understanding of the evolution of microstructure and crystallographic texture at different levels till large deformation of shear strains employed during HPT processing has been developed and will be presented.