Nanoscale microstructures in substitutional solid solutions by large strain machining
Abstract
The deformation field associated with chip formation in machining offers a framework for studying various phenomena associated with very large strain deformation. Plane-strain machining is used to study microstructure changes as a function of strain, temperature, and solute additions in a model material system - substitutional solid solutions of copper. The solid solutions incorporate three different solute additions specifically selected for their differing influences on stacking fault energy (SFE): Ni (increases SFE), Mn (negligible influence on SFE) and Al (decreases SFE). It is shown that a variety of ultra-fine grained (UFG) and nanostructured grains can be created by varying the conditions of strain and temperature. The effect of solutes on the microstructure developed by the large strain deformation is elucidated. The mechanical properties (hardness and yield strength) and thermal stability of the microstructures are characterized. The observations indicate that the SFE plays a negligible role in the microstructure refinement during large strain deformation. The solutes stabilize the nanostructured grains to higher strains and temperatures. Furthermore, the solutes enable a greater refinement of the microstructure, with sub-100 mn grain sizes resulting at the higher strains. It has also been shown that the nanostructured materials continue to undergo further plastic deformation, after their formation; by twinning; a result independent of the SFE of the material. The results have implications for large scale manufacturing of structural nanomaterials for discrete product applications.
Degree
Ph.D.
Advisors
Compton, Purdue University.
Subject Area
Materials science|Metallurgy
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.