Influence of Alloy Additions on the Microstructure, Texture, and Hardness of Low-Pressure Cold-Sprayed Al-Cu Alloys
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Influence of Alloy Additions on the Microstructure, Texture, and Hardness of Low-Pressure Cold-Sprayed Al-Cu Alloys Tian Liu1 • Jeremy D. Leazer2 • Halle Bannister1 • William A. Story1 Benjamin D. Bouffard3 • Luke N. Brewer1
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Submitted: 1 October 2018 / in revised form: 14 March 2019 / Published online: 30 April 2019 Ó ASM International 2019
Abstract This paper examines a series of Al-Cu binary alloy coatings, ranging from 2 to 5 weight percent copper, produced using low-pressure cold spray (CS) deposition with helium as the carrier gas. Binary Al-Cu alloy feedstock powder was produced through inert gas atomization and was sprayed over a variety of temperatures and pressures. Using helium gas, this set of Al-Cu alloys was successfully deposited as high-density coatings. Raising the carrier gas pressure increased the particle velocity and deposition efficiency (DE) in the case of spraying the Al5 wt.% Cu powders. A clear composite deformation structure was formed in all coatings with clear prior particle centers surrounded by severely deformed regions with ultrafine grains. Microstructural deformation generated by the CS process produced a weak but clear \110[ fiber texture for both Al-2 wt.% Cu and Al-5 wt.% Cu coatings. The copper content of the feedstock powder directly influenced the coating hardness and porosity, while having no systematic effect on the DE. Keywords Al-Cu alloy coatings cold spray deposition efficiency fiber texture
& Luke N. Brewer [email protected] Tian Liu [email protected] 1
University of Alabama, Tuscaloosa, AL, USA
2
Naval Postgraduate School, Monterey, CA, USA
3
Naval Surface Warfare Center, Carderock Division, West Bethesda, MD, USA
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Introduction Cold spray (CS) deposition is a relatively new material deposition technique for additive repair of large aluminum structures (Ref 1), which is also part of the large family of thermal spray processes (Ref 2). Unlike conventional thermal spray, cold spray is a solid-state material deposition process in which a supersonic gas jet with a temperature below the melting point of the feedstock material is utilized to accelerate small feedstock powder particles (540 lm) to a high velocity (300-1200 m/s) before impacting them onto a substrate to form a coating via complex plastic deformation and bonding mechanisms (Ref 2). Many studies have now shown successful CS deposition of various kinds of metals and alloys, such as aluminum (Ref 3, 4), copper (Ref 5, 6), and stainless steels (Ref 7, 8). Rokni et al. (Ref 9) have recently reviewed the literature surrounding CS deposition of metallic alloys. Interest in depositing higher-strength aluminum alloys via CS for additive repair and manufacturing continues to grow. The CS additive repair approach could potentially extend the life of structural components, e.g., supersonic particle deposits of AA7075 with good fatigue strength as a structural repair option for aircraft structures (Ref 10, 11). Recent work by Petra´cˇkova´ et al. (Ref 12) showed that the specimen rep
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