Effects of Strain Rate and Annealing Temperature on the Evolution of Microstructure and Texture in Pure Niobium
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INTRODUCTION
THE strain conditions in a metal vary due to different strain parameters during deformation. The microstructure, texture, dislocation arrangements, recrystallization kinetics, and mechanical properties of body-centered cubic (bcc) metals are influenced by the parameters of strain rate, capacity, temperature, and deformation mode. Therefore, many researchers have paid more attention to the control techniques of texture and microstructure during plastic deformation. Many bcc metals, such as tantalum, tungsten, vanadium, and molybdenum, have been investigated to reveal the evolution of texture and microstructure during deformation and recrystallization.[1–6] Christian et al.[7] reported that dislocation mobilities and multiplication rates were important factors to maintain ductility, and the yield stress of bcc metals would increase in lowtemperature deformation conditions. Michaluk claimed that a random texture and homogeneous fine-grained
T.W. XU, S.S. ZHANG, N. CUI, L. CAO, and Y. WAN, School of Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao 266520, Shandong, China. Contact e-mail: [email protected] Manuscript submitted March 28, 2019. Article published online August 22, 2019 METALLURGICAL AND MATERIALS TRANSACTIONS A
microstructure could obviously improve the properties of tantalum.[8] Noell et al.[9] reported that dynamic abnormal grain growth (DAGG) did not appear in recrystallized Mo and that dynamic normal grain growth might be influenced by the crystallographic texture. Niobium is widely used for superconducting applications due to its excellent superconductivity and workability.[10,11] Pure niobium has a bcc lattice structure and exhibits excellent plastic deformation ability. The advanced properties of niobium are strongly dependent on its chemical purity, microstructure, mechanical properties, and physical properties.[12] Researchers seek to obtain reasonable microstructures and textures in niobium through optimization of the manufacturing processing to expand the applications of niobium.[13] The evolution of texture is significantly influenced by the initial textures and the preceding deformation.[14,15] Tensile experiments in niobium nanopillars have revealed the essence of generation and glide of dislocations in some specific slip planes.[16] Srinivasan et al.[17] also found that {001} and {110} textures were stable in cold-rolled niobium and that {111} orientations were prone to recrystallization after annealing. In contrast to monocrystal and bicrystal niobium,[17,18] the deformation and recrystallization behaviors of polycrystalline niobium have complicated deformation mechanisms due to correlative effects of VOLUME 50A, NOVEMBER 2019—5297
the grain interaction.[19] Furthermore, the individual grains in polycrystalline niobium would exhibit distinct deformation and work-hardening behaviors.[20] In this paper, the evolution of microstructure and texture in pure polycrystalline niobium was investigated during compression and recrystallization. The behaviors of def
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