Atomistic Simulation of Nano-Rolling Process for Nanocrystalline Tungsten
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https://doi.org/10.1007/s11837-020-04337-8 Ó 2020 The Minerals, Metals & Materials Society
NANOMECHANICS OF LOW-DIMENSIONAL MATERIALS
Atomistic Simulation of Nano-Rolling Process for Nanocrystalline Tungsten K. VIJAY REDDY1 and SNEHANSHU PAL
1,2
1.—Department of Metallurgical and Materials Engineering, National Institute of Technology Rourkela, Rourkela 769008, India. 2.—e-mail: [email protected]
Nanocrystalline tungsten (NC W) sheets and foils have significant high-temperature applications in various technological sectors and hence their economical large-scale production is highly necessary. However, research to help understand the underlying nanoscale deformation mechanisms is limited. Here, we have developed an atomistic model to study the temperature effect on the structural and grain orientation evolution in NC W during nano-rolling. Structural analysis shows that the contribution of dislocation mechanisms decreases and twin mechanisms increases with an increase in temperature. Moreover, atomic strain analysis revealed that cryo-rolling causes formation of a smoother surface, whereas hot-rolling leads to uneven surfaces. A bimodal grain structure is obtained during the cryo-rolling, whereas equiaxed grains are formed at high temperature due to dynamic recrystallization. This work provides insights into comprehending the deformation mechanisms at atomic level, and the compendium of this research will help in studying nano-rolling in other metallic systems.
INTRODUCTION Advancement in high-temperature applications demands materials with improved mechanical, physical, and thermomechanical properties that are also sustainable under extreme operating conditions. From this perspective, nanocrystalline tungsten (NC W) is an important material as it possesses a very high melting point, superior strength, enhanced thermal conductivity, and good creep resistance.1–6 Wei et al. studied the uniaxial compression behavior of nano-grained W and found deformation to occur in an elastic-perfectly plastic manner.2 Moreover, the strain-rate sensitivity (SRS) was reduced to half the value of the conventional W specimen.2 In another investigation conducted by Zhao et al., strong and nanoporous W sheets have been developed with extremely high strength, which can be utilized for radiation shielding.5 However, in order to utilize this nanoscale material in various applications such as aerospace, military, and radiation industries, the metal has to (Received April 27, 2020; accepted August 17, 2020)
be mass-produced in the form of sheets and foils.1 In addition, controlling and optimization of the crystal texture in the metal sheets is important because some properties, such as irradiation resistance and thermal conductivity, are dependent on grain orientation.7–10 For instance, Miyamoto et al. analyzed blistering behavior in a pure tungsten specimen and found that < 111 > oriented grains tend to form more blisters.7 In order to manufacture textured metallic sheets at a large scale, rolling is the processing technique tha
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