MSE Ph.D. Proposal - Judith Dickson

Date: Monday, February 2

Location: Love, Room 295
Time: 8:00 AM

Committee members:

Dr. Thomas H. Sanders, Jr., (Advisor) MSE

Dr. Naresh Thadhani, MSE

Dr. Hamid Garmestani, MSE

Dr. Richard W. Neu, ME

Mr. Victor Dangerfield, Universal Alloy Corporation

Title: Thermo-mechanical Processing of Aluminum 2195

Abstract:

Al 2195 offers superior properties for many industries as evidenced by its use in the super lightweight external tank for the Discovery shuttle (NASA mission STS-91). Al 2195 is 30% stronger and 5% less dense than the previously used Al 2219; use of Al 2195 resulted in a weight savings of 7,500 pounds [1]. Similar to most lithium containing alloys, however, Al 2195 exhibits significant anisotropy after processing. For complex extrusions, this can result in vastly different properties throughout the cross section. Therefore, particular attention will be paid to characterizing crystallographic macrotexture development. The ability to understand and control anisotropy is paramount to the industrial success of an alloy. Currently, the effects of changing processing variables on texture development and anisotropy are unclear because the mechanisms at play are not well understood. This research focuses on systematically investigating these mechanisms.

For the rolling process, the effect of changing pre-heat time and temperature will be investigated, and for the extrusion process, the aspect ratio, initial billet temperature, and ram speed will be systematically adjusted. Samples will be studied in both the as-processed (F temper) and solution heat treated (W temper) states. Rockwell hardness measurements, tensile tests, microscopy, and texture analysis via x-ray diffraction generated pole figures and orientation distribution functions will all be performed. Optical, scanning electron, and transmission electron microscopy will be used to characterize the microstructure as well as to investigate the interfaces between second phase particles and the matrix. By understanding the microstructure during deformation, this study aims to suggest practices for reducing anisotropy in Al 2195. using this understanding to control the microstructure during thermo-mechanical processing.