Cold-rolling and recrystallization textures of a nano-lamellar AlCoCrFeNi2.1 eutectic high entropy alloy

Wani, I S and Bhattacharjee, T and Sheikh, S and Clark, I T and Park, M H and Okawa, T and Guo, S and Bhattacharjee, Pinaki Prasad and Tsuji, N (2017) Cold-rolling and recrystallization textures of a nano-lamellar AlCoCrFeNi2.1 eutectic high entropy alloy. Intermetallics, 84. pp. 42-51. ISSN 0966-9795

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Abstract

The development of texture during cold-rolling and recrystallization was investigated in a AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA). For this purpose, the as-cast alloy was cold-rolled to 90% reduction in thickness and annealed at temperatures ranging from 800 °C to 1200 °C. The microstructure of the as-cast EHEA showed a nano-lamellar mixture of L12 and B2 phases. The B2 phase was significantly harder than the L12 phase. Development of an ultrafine microstructure was observed after 90% cold-rolling. During cold-rolling, progressive disordering of the L12 phase was observed while the B2 phase maintained the ordered structure. The progressive disordering and development of a predominantly brass type texture in the L12 phase correlated well with profuse shear band formation during cold-rolling. The B2 phase showed the presence of the {111}<110> component which was typical for cold-rolled B2 alloys. An ultrafine duplex structure of equiaxed L12 and B2 phases developed after complete recrystallization that showed significant resistance to grain growth up to very high annealing temperatures (∼1300 °C). The remarkable resistance to grain growth compared to conventional or even other single or dual phase HEAs was due to the formation of a homogeneous duplex structure where growth of one phase was effectively retarded by the other phase. The strong presence of the α-fiber components, but weak BR ({236}<385>) and D ({113}<332>) components in the recrystallization texture of the L12/FCC phase was due to the absence of strong preferential nucleation or growth. Presence of ND-fiber (ND//<111>) with strong {111}<011> component in the recrystallization texture of the B2 phase indicated ease of nucleation from similarly oriented regions in the deformed microstructure.

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