Correlating the Five-Parameter Grain Boundary Character Distribution and Corrosion Behavior of Zinc-Carbon Nanotube Comp
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GRAIN boundary character determines the properties of a material. Grain boundary engineering (GBE) is a popular technique employed to tailor the grain boundary structure in low stacking-fault energy FCC metals such as Ni-based alloys, austenitic stainless steel, and Cu based alloys.[1–9] GBE enhances the fraction of special boundaries such as low R coincidence site lattice (CSLs) boundaries (i.e., R £ 29) via thermomechanical processing (TMP) involving uniaxial tension/compression or rolling followed by annealing. In general, three
K. SAI JYOTHEENDER and CHANDAN SRIVASTAVA are with the Department of Materials Engineering, Indian Institute of Science, Bangalore 560012, India. Contact e-mail: [email protected] Manuscript submitted June 29, 2020, accepted October 14, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS A
parameters corresponding to lattice misorientation are not enough to characterize the grain boundaries. As twins (R3 CSLs in FCC) formed via TMP can be coherent or incoherent twins, they can be differentiated only based on the boundary plane. Therefore, two plane orientation parameters should also be considered. The grain boundary character of a boundary with special properties is generally low index planes and possession of low energies. The energy of the grain boundary varies as a function of five crystallographic parameters. Research studies on grain boundary character distribution (GBCD) on HCP materials are minimal. Randle et al.[10] were the first to conduct studies on titanium alloys. The investigations provided grain boundary distribution details with phase transformation (b to a), suggesting a strong texture with near prism planes. A five-parameter analysis by Beladi et al.[11] reported a strong interface texture which terminated on the prismatic plane {hki0} and a population of intervariant
boundaries belongings to 63.26 deg/[1055 3] and 60 deg/ [1120] misorientations. In the report on casted AZ31 alloy, Beladi et al.[12] suggested that when the grain boundary plane population is not inversely related to the expected grain boundary energies, it could result in the formation of residual columnar grains which remain even after annealing. Kelly et al.[13] reported that in a-Ti, a fraction of grain boundaries with 180 deg-twist and 180 deg-tilt character was more than expected in random distribution. Similarly, grain boundary planes with basal orientation were less common than with prismatic orientation. Studies by Ghamarian et al.[14] provided one of the first reports on the application of five-parameter analysis on thin films characterized using the transmission electron microscopy technique. The studies were done on nanocrystalline a-Zr thin films, and results were compared with a-Ti. In the report by Ram et al.[15] Mg alloy was deformed to promote twinning. When deformed in tension, an extension twin with about 86 deg/[2110] angle/axis misorientation with a (01 12) symmetric boundary plane was formed. Asymmetrical boundary planes with (0 111) and (01 13) orientation were reported fo
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