Stress Corrosion Cracking Resistant Aluminum Alloys: Optimizing Concentrations of Alloying Elements and Tempering

Abstract

The objective of this study is to develop a new family of aluminum alloys with superior stress corrosion cracking resistance (SCCR) and mechanical properties. This approach uses experimentally obtained stress corrosion resistance, tensile strength, and yield strength data from the literature and then performs hybrid multiobjective evolutionary optimization combined with multidimensional response surfaces. This software has the proven capability to deal with various alloy design applications using minimal amount of experimental data. The selected objectives in this study are superior stress corrosion resistance, tensile strength, and yield strength. The design variables are concentrations of alloying elements and the individual alloy tempers as they are important parameters that directly affect macroscopic properties and microscopic details of the alloy such as grains, phases, precipitates, etc. The computational trials yield optimal alloys' chemical compositions and standard thermal treatment protocols for the best combination of superior stress corrosion resistance and mechanical properties. Single-objective optimization results confirm the known experimental observations that dilute Al alloys yield the best corrosion resistance at the expense of tensile strength. Optimizations with two simultaneous objectives and more alloying elements create better trade-off solutions. Quality and number of initially available experimentally evaluated alloys have decisive effects on accuracy of this alloy design method.

Keywords:

• Alloy design
• Alloy optimization
• Alloy tempering
• Aluminum alloys
• Stress corrosion

ACKNOWLEDGMENTS

This work was supported by the U.S. Office of Naval Research under a STTR Phase-I (contract N68335-08-C-0325-FIU-001) and under a SBIR Phase-I (contract N00014-09-M-0415-FIU-001) funding monitored by Dr. William Frazier. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the U.S. Office of Naval Research or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for government purposes Notwithstanding any copyright notation thereon.