Texture development in axisymmetric forging and plane strain compression of lithium fluoride

Keith Larry Kruger, Purdue University

Abstract

Although many of the fundamental deformation mechanisms which lead to the development of crystallographic textures in polycrystals are recognized, knowledge of the activity and interactions of these mechanisms is limited in systems with significant plastic anisotropy. Dislocation motion is a primary mechanism enabling deformation to occur during processing of most crystalline materials, and carries with it the potential for the formation of crystallographic textures. However, highly anisotropic and slip-limited systems, such as many ceramics and geological materials, have few potential dislocation slip systems. Further, at the temperatures necessary to activate dislocation slip other mechanisms may be active that are more difficult to model (e.g., recrystallization). Lithium fluoride, a cubic material that exhibits strong plastic anisotropy typical of other ceramics, was used to examine texture development of polycrystals together with the associated effects on microstructure. The strength of this research lies in the control of the critical parameters of displacement rate, temperature, and purity level for two deformation geometries, and with characterization of the resulting textures and microstructures. Substantial differences developed in the texture components during axisymmetric forging at different dopant levels. Similar experiments in plane strain compression revealed few differences in texture development. Evaluation of the experimental data and comparisons to existing literature suggest that texture development is controlled by both polygonization-based dynamic recrystallization and dislocation slip. The nature and type of textures observed between the two deformation geometries indicates that a strong interaction exists between the two mechanisms. The experimental data are intended to provide a physical basis for evaluating model results that correlate the crystallographic textures with the deformation behavior of the polycrystal.

Degree

Ph.D.

Advisors

Bowman, Purdue University.

Subject Area

Materials science

COinS