Achieving Superior Strength and Ductility Combination Through Cryorolling in 2219 Aluminum Alloy
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JMEPEG https://doi.org/10.1007/s11665-020-05124-x
Achieving Superior Strength and Ductility Combination Through Cryorolling in 2219 Aluminum Alloy K. Sivaprasad, B. Blessto
, V. Muthupandi, and M. Arumugam
(Submitted February 20, 2020; in revised form July 17, 2020) In aluminum 2219 alloy, a combination of ultra-fine grains and coarse grains was established through cryorolling. Formation of bimodal grain distribution was confirmed using electron backscattered diffraction analysis, transmission electron microscopy and x-ray diffraction analysis. Cryorolled samples showed a 3% increase in strength, with a 4% increase in ductility. An increase in dislocation density, reduced slip distance and bimodal grain structure were attributed to the strength–ductility combination. Dislocation annihilation rate and driving force for dislocation movement were also determined based on the temperature of deformation and dislocation density in rolled material. The unidirectional and cross-directional cryorolled samples resulted in a grain size ranging from 510 nm to 73 lm and 340 nm to 42 lm, respectively. Keywords
AA2219, aluminum, cryorolling, dislocation annihilation rate, microstructure, rolling, texture
1. Introduction Ultra-fine grains (UFG) are produced either by sintering powders into alloy through deposition/ball milling or by introducing a high amount of dislocation density on a dense polycrystalline material through plastic deformation (Ref 1). Severe plastic deformation (SPD) processes are certain to increase the strength in room temperature and ductility at elevated temperatures (Ref 2). The ultra-fine-grained material tailored by these SPD processes was found to have applications in various severe environments. Though they provide a decent ductility at high temperatures, their plastic properties are inadequate in the working environment. A combination of high strength and ductility (Ref 3) in the material is very much desirable for industrial applications. For optimizing the expected mechanical properties, changes happening during recovery and recrystallization are notable (Ref 4-6). Several mechanisms like a combination of plastic deformation processes (Ref 7), activating micro-shear banding (Ref 8-10) and tailoring second phase particles in a fine-grained metal matrix (Ref 11) have been accustomed by researchers to achieve high strength and ductility. Cryorolling, one of the plastic deformation technique, is a research area of interest in recent years. This processing method offers improvement in mechanical properties for less applied strain by the formation of ultra-fine grains (UFG < 10 lm) (Ref 1, 7, 12). The development of a bimodal grain structure is an effective way of obtaining necessary K. Sivaprasad, B. Blessto, and V. Muthupandi, Advanced Materials Processing Laboratory, Department of Metallurgical and Materials Engineering, National Institute of Technology, Tiruchirappalli 620015, India; and M. Arumugam, Liquid Propulsion Systems Centre, Thiruvananthapuram 695547, India. Contact e-mail: [email protected].
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