Thursday, March 19, 2015
Goldwater Center 487, Tempe campus [map]
Magnesium (Mg), particularly in sheet form, opens up entirely new possibilities for lightweighting in the automotive and aerospace industries. However, widespread application of Mg sheet has been mainly limited due to its low workability, both in primary sheet processing by rolling and secondary sheet forming. This talk describes a new hybrid extrusion-machining method for processing Mg alloy into bulk sheet and foil forms in a single deformation stage. By utilizing a constraining edge placed across from the tool cutting edge, the usual machining process is transformed into a continuous shear deformation process, wherein the geometry and dimensions of the chip (sheet) at its exit from the deformation zone are directly controlled. The confinement of deformation field in extrusion-machining enables near-adiabatic heating in the deformation zone and efficient utilization of plastic-deformation work. Consequently, pre-heating of the workpiece, intrinsic to Mg sheet processing by rolling, is minimized. The deformation field parameters such as strain, strain path and strain rate can be independently controlled to induce severe microstructure refinement, and engineer crystallographic textures that are radically different from that in rolling. A detailed application of parametric deformation control to create tilted-basal textures and ultrafine grain sizes in Mg sheet for enhanced combinations of strength and formability is presented. Furthermore, since extrusion-machining is a single-stage process for sheet production, it is potentially attractive in terms of production economics and energy. Implications for process scale-up and control of plastic flow localization are also briefly discussed.
Sagapuram is a postdoctoral research associate in the Center for Materials Processing and Tribology at Purdue University. He received B.Tech. and Ph.D. degrees in Materials Engineering from Indian Institute of Technology Madras (2009) and Purdue University (2013), respectively. His research and teaching interests are in materials processing, mechanical behavior, experimental mechanics and manufacturing. He has co-authored 10+ journal and conference papers, and 2 U.S. patent applications in these areas. Dr. Sagapuram was a recipient of the TMS Light Metals Division Magnesium Technology Award (2012), and Indiana state winner in the U.S. DOE’s Clean Energy Challenge business plan competition (2012).