Effect of hot rolling deformation on microstructure and mechanical properties of pure cobalt
In order to study the effect of different hot rolling deformations on the microstructure and mechanical properties of pure cobalt,high-purity cobalt(99.95%)was hot-rolled at 500℃,and the rolled samples were characterized by XRD and EBSD after water cooling.The results show that the annealed initial state sheet has two-phase structure of HCP phase and FCC phase,with HCP phase being the main component.With rolling process,the grain size is refined from 28.08 µm to 12.35 µm,the content of ∑3 annealing twin bounady and phase transition twin boundary decreases,the residual strain increases,and the dislocation accumulates continuously,two-phase content changes,FCC phase content increases,and HCP phase content decreases.The grain boundaries of different phases exhibit the same trend of change with the increase of low angle grain boundaries(LAGB)content and the decrease of high angle grain boundaries(HAGB)content.Under different reduction amount,the performance of pure cobalt sheet with 27%reduction amount is the best.At this time,the yield strength,tensile strength,hardness and elongation of pure cobalt(657.18 MPa,964.05 MPa,298.2HV0.5,42.87%)are improved compared with the initial state(408.34 MPa,862.53 MPa,214.4HV0.5,38.07%).The plasticity of cobalt does not decrease but increases with the increase of the strength,mainly due to the increase of FCC phase content and the refinement and homogenization of large-sized grains in layered HCP phase.
pure cobalthot rollingmicrostructuremechanical property
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