Study of grain refinement in Al alloy 2519 using backscatter orientation-contrast mode in the scanning electron microscope
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Authors
Dunlap, Jeffrey Robert
Subjects
Aluminum-copper alloys
Grain refinement
Particle stimulated nucleation (PSN)
Grain refinement
Particle stimulated nucleation (PSN)
Advisors
McNelley, Terry R.
Crooks, Roy
Date of Issue
1992-12
Date
December 1992
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
The effects of variations in thermomechanical processing (TMP) parameters on grain refinement in 2519 Al-Cu alloy were studies. Refined grains enhance tensile ductility and are a prerequisite for superplastic response. The TMP variables were adjusted based on particle stimulated nucleation (PSN) theory. Process modifications included increases initial overaging time and decreased subsequent warm rolling temperatures. Backscatter orientation-contrast (BSOC) techniques for the scanning electron microscope (SEM) were developed to achieve grain-orientation contrast. An accelerating voltage of SKV resulted in increased intensities for atomic number and orientation contrast. Both grains and 0-phase (Al(2)Cu) precipitates were revealed on the same micrograph at high resolutions than attainable in the optical microscope. Quantitative data from micrographs were obtained using image analysis methods. A method based on statistical considerations was developed to determine an approximate critical 0-phase particle diameter(d(crit)) for PSN. The 0-phase particle distribution was shown to be an important factor from grain refinement via PSN..
Type
Thesis
Description
Series/Report No
Department
Mechanical Engineering
Organization
Naval Postgraduate School
Identifiers
NPS Report Number
Sponsors
Funder
Format
51 p.
Citation
Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.