Towards Process-Specific Alloys for Improved Corrosion and Mechanical Properties of Cold Spray Repairs to Naval Al-Mg Alloys
Abstract
Cold gas dynamic spray (cold spray) is an emerging technology capable of producing fully dense deposits at high rates in ambient atmospheres for in situ repair. However, its application to 5XXX-series aluminum alloys for Naval structures has been limited due, in part, to the highly cold worked, fine-grained deposit microstructure causing low ductility. This project will explore the fundamental interactions between Mg content, dislocation density, and grain structure on the balance of strength, ductility, and atmospheric corrosion susceptibility of cold spray deposited Al- Mg binary alloys. Naval structural aluminum, such as AA5083, relies on a supersaturated Mg matrix to meet mechanical design criteria, which also unfortunately provides a driving force for precipitation of electrochemically active Al3Mg2 (beta-phase) particles at grain boundaries (called sensitization) leaving Al-Mg alloys susceptible to intergranular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC). The complex microstructure produced during cold spray deposition may change the balance of strengthening mechanisms within a material, thereby reducing the need for supersaturated Mg solution. This project will systematically evaluate the influence of Mg content in the cold spray feedstock powders on the individual and combined effects of strengthening mechanisms and sensitization. Custom Al-Mg powders with a range of Mg content will be fabricated in-house by gas atomization. Dislocation density will be controlled by processing parameters and feedstock powder Mg content. The project is divided into tasks involving powder metallurgy and cold spray processing, sensitization kinetics, mechanical metallurgy, and simulated atmospheric corrosion that will be completed using advanced microscopy, tensile testing, and electrochemical methods. The scientific knowledge produced here will increase fundamental understanding of the complex interactions between cold spray deposited microstructure, strengthening mechanisms, and sensitization kinetics. The complex microstructure of cold-sprayed material may provide an opportunity to mitigate susceptibility to IGC and IGSCC through reduction of the required Mg composition while maintaining acceptable ductility without decreasing the strength of the material. These results will advance the application of cold spray for in situ repair of Naval components.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 09, 2021
- Source ID
- N000142112459
Entities
People
- Gregory Kubacki
Organizations
- Office of Naval Research
- United States Navy
- University of Alabama