Effect of titanium additions on aging characteristics and stress corrosion cracking susceptibility of Al-Zn-Mg alloys
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Authors
Chʻen-chün
Issue Date
1977-05
Type
Electronic thesis
Thesis
Thesis
Language
ENG
Keywords
Physical metallurgy
Alternative Title
Abstract
A study has been made on the effect of Ti additions on the microstructure in aging treatments and stress corrosion cracking (SCC) susceptibility of AI-Zn-Mg alloys. The influence of aging treatment was examined for alloys with and without Ti addition. For two-stage aging treatments, the alloys were solution heat treated at 510℃, air cooled, then aged at various temperatures below the G.P. zone solvus for short times before aging above the G.P. zone solvus at 200℃. The Ti addition alloy yields a small precipitate-free zone (PFZ (~ O.3μ) and a higher density of precipitate near the edge of the PFZ than in the mid-grain region. The ternary alloy ·without Ti addition produces a wide range of PFZ sizes (0.4 to 4μ) depending upon the aging temperature below the G.P. zone solvus. Significant changes in the morphology of the matrix precipitate, the amount of grain boundary precipitate, and the width of PFZ, were observed in single stage aging at 200℃ as a result of the Ti addition. These results could be explained in terms of Ti interacting with vacancies or solute atoms, causing the changes in the vacancy and/or solute concentration profiles. A model based upon solute and vacancy concentrations coupled with a time at temperature effect has been developed to allow the interpretation of the observed two-stage aging results in an Al-Zn-Mg alloy.
Description
May 1977
School of Engineering
School of Engineering
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY