Materials Frontier No.126
Title:Producing layered nano-composite structures by accumulative roll bonding
Speaker:Dr.Md Zakaria Quadir, Australian National Scientific Officer, Electron Microscope Unit Lecturer, School of Materials Science and Engineering, the University of New South Wales, Australia.
Venue: Room.308, Material Building A
Inviter: Prof.Deliang ZHANG
Dr M Z Quadir is a materials research manager in electron microscope unit (EMU) and lecturer in the school of materials science and engineering in the University of New South Wales (UNSW) of Australia. Quadir received a metallurgical engineering degree in 1997 and obtained a PhD degree in 2003 from the University of Hong Kong (HKU). Then he continued postdoctoral research in HKU for three more years before joining UNSW in 2006. Quadir provides research and technical leadership in physical science projects within EMU in the areas of materials science, mechanical engineering, electrical engineering and photovoltaic research. Quadir has published over sixty peer reviewed research articles in the field of electron microscopy, thermo-mechanical processing, electronic-packaging, alloy-design, textures, recrystallization and grain growth. As an indication of academic impact, his articles attracted over 170 citations in the last three years.
Accumulative roll bonding (ARB) is a recently developed severe plastic deformation technique to incorporate nano-crystalline structures in bulk metal sheets. In this investigation, conventional and layered hybrid structures were generated by ARB processing. The texture and microstructure of the central and subsurface regions were studies by high resolution scanning electron microscopy (SEM) and electron back scattered diffraction (EBSD) techniques. After each ARB cycles, the through thickness spatial distribution of textures and microstructures of the sheet was analyzed. A complementary embedded scratch test investigation was also conducted to find the thickness dependent redundant shear strain of each layer. The changes in the scratch trajectories during the subsequent ARB cycles were also monitored to find the changes after each cycle. It was found that the redundant shear strain distribution has a strong influence on the textures and microstructures in the earlier ARB cycles. The orientation of materials near the bonding region is governed by the redundant shear strain, which gradually diminishes near the middle thickness, which is away from the bonding interface, where the typical beta fibre rolling texture dominates. Redundant shear has a pronounced effect in hybrid ARB sheets. With increasing ARB cycles the through thickness texture becomes homogeneous. It is also eminent that the high redundant shear strains of earlier ARB cycles have strong consequence on the overall texture formation and subsequent recrystallization.