Bulk Nanocomposites Produced by Thermally Activated Severe Plastic Deformation

In this paper, several versions of extrusion processes were used to provide severe plastic deformation for grain refinement (with a modified ECAE extrusion) and for grain/fiber alignment (with straight extrusion). The process was performed at elevated temperatures to reduce extrusion pressure, and in order to increase strength and avoid grain growth secondary phases were added or insitu formed. In addition, this study also attempt to develop a one-step material synthesis and net-shape forming technique for shape memory alloys, which starts at elementary metals and the chemical reaction synthesis was triggered at a low temperature (400-600 C) and with sustained reaction. The generated heat was used for compression or extrusion to form desired final components at improved properties. The produced materials were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In order to understand the process and microstructure alignment, several modeling methods were used, including analytical and finite element methods. The potential for extending this process for manufacturing smart materials with improved performances, such as shape memory effect of nano-grained shape memory alloys in many MEMS and sensor applications, is also discussed.