Masters Theses

Keywords and Phrases

Friction stir process

Abstract

"Friction stir processing (FSP) is a successful solid state processing technique for microstructural modification of metals based on the principles of friction stir welding (FSW). Commercial A1 castings are normally modified using heat treatment or chemical modifiers, but these methods are not successful in removing cast porosity or achieving high ductility results. Cast A1 alloy A3 56 plates have been successfully modified by FSP to enhance mechanical properties, including substantial increases in ductility, but only with 0.25” tool diameters. The aim of this study was to expand the range of tooling sizes used for FSP and optimize the process parameters for relatively large toolings, while further studying the effects of FSP on the cast microstructure. The process windows for tools 0.375” and 0.50” were found to be significantly narrower than those reported for smaller tools, showing that the process requires much greater control as tooling size increases. Defects formed were characterized in categories established in FSW research. Microstructural changes were similar to those previously reported, but larger tools create a slightly less homogeneous microstructure. Transmission electron microscopy (TEM) studies were conducted, and the Si particle morphology was studied. FSP was shown to be successful at solutionizing intergranular Si and precipitating grains at a high rate, creating a finer microstructure. TEM of FSPed material also showed the creation of high angle grain boundaries, suggesting that a wrought-like microstructure has been successfully embedded into the casting"--Abstract, page iii.

Advisor(s)

Mishra, Rajiv S.

Committee Member(s)

Richards, Von
Dharani, Lokeswarappa R.

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Metallurgical Engineering

Comments

The author thanks the Defense Advanced Research Projects Agency for funding this research under contract No. MDA972-02-C- 0030.

Publisher

University of Missouri--Rolla

Publication Date

Fall 2004

Pagination

ix, 43 pages

Note about bibliography

Includes bibliographical references (pages 40-42).

Rights

© 2004 Martin Anthony Rust, All rights reserved.

Document Type

Thesis - Restricted Access

File Type

text

Language

English

Subject Headings

Aluminum alloys
Aluminum alloys -- Microstructure

Thesis Number

T 8590

Print OCLC #

57936366

Link to Catalog Record

Electronic access to the full-text of this document is restricted to Missouri S&T users. Otherwise, request this publication directly from Missouri S&T Library or contact your local library.

http://laurel.lso.missouri.edu/record=b5282295~S5

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