Further Studies of Directional Recrystallization Processing

Dartmouth College, Hanover NH

Investigators

Abstract

This project is a fundamental study of directional recrystallization processing, the process whereby one or a few grains or crystals nucleate at one end of a specimen and grow along with a moving hot zone. Directional recrystallization has a number of advantages: net-shape processing; potential energy and cost savings compared to directional solidification; and the ability to process materials not amenable to directional solidification. The overall goal is to understand how key microstructural parameters (the size and spacing of particles, and the grain size and orientation) interact with the processing conditions (rate of hot zone movement and temperature) to control the microstructure. How the initial microstructure and processing conditions can be exploited to produce columnar grains or single crystals of a particular orientation will be explored in polycrystalline nickel sheets. The role of particles will be examined in a model system of copper (both single crystals and polycrystals) containing finely-dispersed particles that can coarsen during processing. Determining the role of particle coarsening or dissolution is key to understanding how columnar grains or single crystals can be produced in many commercial alloy systems. The work will involve a close coupling of experiments with computational microstructural simulation of the processing utilizing a front-tracking grain growth model. While working on specific materials, the goal is to understand directional recrystallization processing at a fundamental level so that this generic technology and the associated modeling can easily be applied to many materials. In addition to graduate education, activities with the Women in Science Project and / or Dartmouth Presidential Scholarships will be encouraged to expand participation of a diverse group of undergraduates on this project. In addition, material developed with the aid of a high school teacher will be presented to high school students.