Dynamic Abnormal Grain Growth and the Production of Single Crystals

University Of Texas At Austin, Austin TX

Investigators

Abstract

TECHNICAL: An experimental investigation will be conducted into dynamic abnormal grain growth (DAGG) and the newly-discovered phenomenon of large single crystal creation by DAGG. It was recently discovered in the PI's laboratory that DAGG can create large single crystals in commercial-purity Mo sheet materials. Preliminary investigations have created Mo single crystals several centimeters in length at far lower temperatures (1300-1500 C) and in much shorter times (minutes) than is possible by conventional single crystal growth methods. These preliminary investigations have raised a number of important fundamental and technological questions which this investigation will seek to answer. Chief among the technological questions are: 1. What ranges of product forms can be produced as single crystals through DAGG, and 2. What materials can be produced in single-crystal form through DAGG? Chief among the fundamental questions are: 1. What is the mechanism of DAGG, and 2. How does plastic straining during DAGG overwhelm most of the factors noted in the literature to limit static abnormal grain growth (SAGG)? Single-crystal production in commercial-purity Mo sheet has been demonstrated, and these investigations will study single-crystal formation in other product forms, notably rod and continuous wire lengths. The ability of DAGG to form single crystals in materials other than Mo will also be investigated, particularly in W and Fe-3%Si. NON-TECHNICAL: Research will impact the field of metallurgy by producing an improved understanding of DAGG and of abnormal grain growth processes in general. The new single-crystal production technologies to be created, particularly for application to refractory metals, is likely to revolutionize the process furnace industry and could potentially replace the W and Mo wire materials used across numerous industries, such as in incandescent light bulbs. Subsequent application to other materials is expected to produce additional impacts and benefits. In addition to existing partnerships, new partnerships will be sought with industry and national laboratories to advance this technology and to better train students participating in the proposed research. The investigations will integrate research, training, and education by including graduate students and undergraduate students in laboratory research and direct training and mentoring under the PI. Particular emphasis will be placed on training and mentoring of undergraduate students and on the recruiting of students from groups underrepresented in engineering for inclusion in the project. Results of the proposed research will be used for instructional materials in both undergraduate and graduate courses. An outreach program to a local elementary school will be enhanced and supported under the proposed project; this outreach program is organized by an honors society for which the PI is faculty adviser. The project will support the continued maintenance and development of unique high temperature mechanical testing facilities at the proposing institution. All research results will be disseminated through publications in peer-assessed journals and presentations at national and international professional meetings; both graduate and undergraduate students will be involved in the dissemination of research results as a part of their training. Societal impacts of the proposed investigation will include teaching and training of students and the creation of a completely new and useful technology.