Experimental optimization of microstructure and mechanical properties of friction stir processed materials

Author

Vikas Dixit

Abstract

"The microstructural evolution and ensued mechanical properties in friction stirred Al-2024 alloy depend upon both process parameters and initial temper. Precipitation strengthened Al-2024 alloy under two different initial tempers; T3 and T8 was used. Material was friction stirred at different sets of tool rotation rate and traverse speed and resultant microstructure was evaluated in the nugget region and heat affect zone (HAZ) using differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and optical microscopy. DSC studies confirmed that initial temper does not affect the microstructure in the nugget region. Calculation of different heat-effects for the processed samples of Al-2024 (T3) alloy revealed the formation energy of GPB zone equal to -231 J/g. Quantitative analysis of precipitation showed a complex variation in the volume fractions of GPB zone and S phase precipitates in the regions of interest. TEM micrographs revealed the coarsening of grain-structures and precipitates at higher thermal cycle. Tensile properties in HAZ were found to be higher than those in nugget, which was attributed to the presence of fine S phase precipitates. In the nugget region, highest tensile strength was achieved for the range of heat-index values close to 10, because of the minimum volume fraction of coarse S phase precipitates. For T3 initial temper, tensile properties in HAZ achieved maximum between 10 and 15 heat-index values; however for the T8 initial temper, they monotonically decreased. Experimental data was utilized to model the yield strength in different regions of interest by using the constitutive equations of different strengthening mechanisms"--Abstract, page iv.

Advisor(s)

Mishra, Rajiv S.

Committee Member(s)

Richards, Von
Krishnamurthy, K.

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Materials Science and Engineering

Sponsor(s)

U.S. Air Force Research Laboratory

Publisher

University of Missouri--Rolla

Publication Date

Summer 2006

Journal article titles appearing in thesis/dissertation

• Effect of initial temper on the mechanical properties of friction stir welded Al-2024
• Influence of process parameters on microstructural evolution and mechanical properties in friction stirred Al-2024 (T3) alloy

Pagination

ix, 58 pages

Note about bibliography

Includes bibliographical references.

Rights

© 2006 Vikas Dixit, All rights reserved.

Document Type

Thesis - Restricted Access

File Type

text

Language

English

Subject Headings

Aluminum alloysCalorimetryFriction welding

Thesis Number

T 8924

Print OCLC #

79845187

Electronic OCLC #

1079365212

Recommended Citation

Dixit, Vikas, "Experimental optimization of microstructure and mechanical properties of friction stir processed materials" (2006). Masters Theses. 3839.
https://scholarsmine.mst.edu/masters_theses/3839