Superior Strength with Enhanced Fracture Resistance of Al-Mg-Sc Alloy Through Two-Step Cryo Cross Rolling
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INTRODUCTION
COMMERCIAL 2000 series aluminum alloys have been recognized as a high-performance structural material for aerospace applications.[1] Recently, Al-Mg alloys with a trace amount of Sc have been considered as a novel high-performance material for aircraft fuselage components, which could reduce the weight by 4 pct with no design change.[2] The addition of Sc instigates the formation of coherent nano-sized Al3Sc dispersoids, which in turn contributes a strengthening effect on the
S. VIGNESHWARAN and R. NARAYANASAMY are with the Department of Production Engineering, National Institute of Technology, Tiruchchirappalli, Tamil Nadu 620 015, India. Contact e-mail: [email protected] K. SIVAPRASAD is with the Advanced Materials Processing Laboratory, Department of Metallurgical and Materials Engineering, National Institute of Technology, Tiruchchirappalli, Tamil Nadu, 620 015, India. Contact e-mail: [email protected] K. VENKATESWARLU is with the Materials Science Division, CSIR-National Aerospace Laboratories, Bengaluru, Karnataka, 560 017, India. Manuscript submitted January 7, 2019. Article published online May 8, 2019 METALLURGICAL AND MATERIALS TRANSACTIONS A
Al-Mg alloy along with grain structure stabilization.[3,4] Apart from the strength enhancement, the benefits of adding Sc to the Al-Mg alloy are the notable improvements in formability and ductility,[5–7] better thermal stability,[8] restriction to recrystallization[9,10] and fracture resistance ability due to the fine-grained microstructure.[11–13] On deforming the Al-Mg-Sc alloy containing Zr in cryogenic condition, enhanced mechanical properties have been observed because of the grain refinement. Furthermore, no ductile-to-brittle transition was reported at 77 K by Zhemchuzhnikova et al.,[14,15] which proves that the Al-Mg-Sc alloy can exhibit ductility even in the cryogenic environment. Cryorolling has been one of the established techniques to produce bulk ultrafine-grained (UFGed) Al alloys,[16–23] Cu alloys[24] and a few other metals.[25–27] Our recent work on the rolled Al-Mg-Sc alloy at room (RT) and cryogenic temperatures (CTs) produced a bimodal microstructure, which shows enhanced mechanical properties and a fracture resistance ability after cryorolling.[28,29] Another study on cross rolling of Cu-Zn brass[30] at CT resulted in the formation of a homogeneous UFGed microstructure with a marginal betterment in mechanical properties compared with the
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unidirectional cryorolled material. Similarly, Xing Pin et al.[31] reported that cross rolling produces a homogeneous microstructure and strong crystallographic texture compared with unidirectional rolling. On the other hand, Suwas et al.[32] determined that the progressive weakening of texture on cross-rolled Cu alloys is higher compared with the unidirectional rolled alloy after post-annealing treatment. However, on increasing the cross rolling reduction in Al alloys, Liu et al.[33,34] found a b fiber formation with a strong brass (notated as Bs) component and a reduction in the
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