Mechanical Behavior and Deformation Kinetics of Aluminum Alloys Processed through Cryorolling and Subsequent Annealing
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ERE plastic deformation (SPD) is used to produce high-strength metallic materials by severe grain refinement.[1] The grain refinement is primarily due to the dislocation accumulation leading to the formation of high-angle grain boundaries (HAGBs). One of the methods to augment the dislocation multiplication is to suppress the dynamic recovery by lowering the deformation temperature to cryogenic levels.[2] This method is especially suitable for aluminum alloys with high recovery due to increased stacking fault energy (SFE). Significant past research has been conducted on different Al alloys to obtain high-strength materials through various deformation techniques at a cryogenic temperature such as cryorolling (CYR),[3] asymmetric
KANDARP CHANGELA and RAVI KUMAR DIGAVALLI are with the Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, 110016, India. Contact email: [email protected] HARIHARAN KRISHNASWAMY is with the Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India. Manuscript submitted June 28, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
CYR,[4] cryo-ECAP,[5] and cryoforging.[6] Among these, CYR constitutes an interesting thermomechanical processing route for sheet metal application, which induces significant microstructural refinement and enhances mechanical strength.[7] In 2002, Wang et al.[8] initially performed CYR of pure copper and obtained a high-strength ultrafine-grained (UFG) structure with sufficient ductility. It is well known that high dislocation density structure plays a major role in refining the microstructure during CYR.[9] However, the as-cryorolled alloys exhibit poor ductility at room temperature, which limits their industrial applications. The ductility, however, can be improved to a great extent by subsequent low-temperature annealing treatment without sacrificing the maximum strength obtained. Aluminum alloys have gained considerable attention in recent years. Many extensive studies have been done in the past to simultaneously improve the strength and ductility by optimizing the heat treatment cycle for pure Al and Al alloys.[10] Recently, Dhal et al.[11] studied the mechanical properties and microstructural behavior of commercially pure Al subjected to CYR and subsequent annealing at 150 °C for 30 minutes. It was found that the good combination of strength and ductility was achieved by
controlled annealing of cryorolled samples leading to a significant improvement in strain hardening capability. Lee et al.[12] systematically studied the influence of annealing temperature (in the range of 150 °C to 300 °C) on the mechanical and microstructural behavior of cryorolled AA 5083. Optimization of CYR and subsequent annealing processes resulted in a mixture of equiaxed grains of size < 200 nm with elongated subgrains exhibiting a good combination of high strength and uniform elongation. A similar alloy was recently studied by Feyissa et al.[13] and a bimodal grain structure was observed. Panigrahi
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