Doctoral Dissertations


Friction stir welding (FSW) is a recently developed process for welding aluminum alloys that has expanded into applications other than welding by the concept of friction stir processing (FSP). Through FSP, it has been found that the properties of materials can be enhanced whether by inserting forged microstructure into a casting, consolidating regions of a part produced by powder metallurgy, or by producing materials with properties which allow them to be formed more easily to name just a few of the applications.

The ability of FSP to alter the microstructure of material has lead to its expansion as a method for creating superplastic material. While some studies have been performed to determine the enhancement of tensile elongations in the nugget region, the understanding is limited and an understanding of the effects of using multiple passes to cover large areas is still needed.

This study examines the use of FSP to make commercial alloys superplastic by altering their microstructure. Not only is the understanding of the single pass process studied in more detail but the effects of using multiple passes of FSP are examined. In the single pass study it was found that the formability of 6061 A1 alloy was enhanced with FSP. Multiple pass work on 7075 A1 alloy found that the process could be expanded to multiple, overlapping passes of FSP and create material which was superplastic with properties with elongations just slightly less than those of the single pass regions. Multiple passes were also performed on 5083 A1 followed by a rolling schedule to increase the achievable elongations possible in the material.

In addition to the examination of FSP for superplasticity, the use of FSP for the addition of carbon nanotubes into aluminum was also evaluated. It was found that the nanotubes were able to survive the harsh conditions of FSP but ideal increases in properties were not seen in the new composites"--Abstract, page iv.


Mishra, Rajiv S.

Committee Member(s)

Miller, F. Scott, 1956-
Krishnamurthy, K.
Kohser, Ronald A.
Newkirk, Joseph William


Materials Science and Engineering

Degree Name

Ph. D. in Metallurgical Engineering


National Science Foundation (U.S.)


The authors gratefully acknowledge the support of the National Science Foundation through the grant DMI - 0323725.


University of Missouri--Rolla

Publication Date

Summer 2006

Journal article titles appearing in thesis/dissertation

  • High strain rate superplastic properties of 7075 aluminum via friction stir processing
  • Multiple passes of friction stir processing for the creation of superplastic 7075 aluminum
  • Use of friction stir processing prior to cold rolling for enhanced superplasticity in AA5083 Al
  • Enhanced formability of 6061 aluminum through friction stir processing
  • Survivability of single-walled carbon nanotubes during friction stir processing
  • Friction stir processed multi-walled carbon nanotubes


xiii, 160 pages

Note about bibliography

Includes bibliographical references.


© 2006 Lucie Beth Johannes, All rights reserved.

Document Type

Dissertation - Restricted Access

File Type




Subject Headings

Aluminum alloys -- Welding
Friction welding
Superplastic forming (Metal-work)

Thesis Number

T 9011

Print OCLC #


Electronic OCLC #


Link to Catalog Record

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