C.C. Gupta

Bio: C.C. Gupta is an academic researcher from Bhabha Atomic Research Centre. The author has contributed to research in topics: Deformation (engineering) & Strain rate. The author has an hindex of 2, co-authored 2 publications receiving 52 citations.

Characterization of superplastic behaviour in the (α + β) phase field of Zr–2.5 wt.%Nb alloy

Abstract: The effect of grain size on superplastic deformation in Zr–2.5 wt.%Nb was studied by constructing processing maps (which depict the variation of strain rate sensitivity with temperature and strain rate) in the temperature range of 650–830 °C and strain rate range of 5 × 10 −6 to 2 × 10 −3 s −1 . The occurrence of superplastic domain with respect to temperature and strain rate was identified for three grain sizes (4, 10 and 16 μm). The 4 μm grain size material exhibited a domain centered around 800 °C and 10 −4 s −1 , exhibiting a ductility of 700%. With increasing grain size the domain shifts to higher temperatures and lower strain rates. A detailed characterization of deformed microstructure revealed equiaxed grain structure (curved boundaries) with considerable grain growth within the superplastic domain. Creep equation was used to evaluate the parameters of superplastic deformation, which resulted in activation energy of 125 kJ/mol and a grain size exponent of 1.6. The accommodation mechanism for superplastic deformation was deduced to be either non-conservative jog motion or grain boundary migration, with the rate controlling step for both being the grain boundary diffusion of Zr and Nb in β phase.

Influence of fraction of high angle boundaries on the mechanical behavior of an ultrafine grained Al–Mg alloy

Abstract: The mechanical behavior of ultrafine grained AA5052 processed through different techniques—rolled, annealed, friction stir processed (FSP) and equal channel angular pressed (ECAP)—were compared and correlated with microstructure. The microstructure was characterized using electron back scattered diffraction to obtain the boundary spacing, the fraction of high angle boundaries and to estimate the dislocation density from local misorientations. Both FSP and ECAP conditions had ultrafine boundary spacing, but the fraction of high angle boundaries was larger for the FSP condition. Tensile deformation carried out at 297 K and 10−3 s−1 showed a lower work-hardening rate and recovery rate for FSP as compared to the ECAP condition. It was inferred that low angle boundaries are more effective sinks for dislocations. When comparing differently processed materials, the strength, ductility and work-hardening behavior correlate better with the fraction of high angle boundaries than the boundary spacing.

Mechanical Properties, Dislocation Density and Grain Structure of Ultrafine-Grained Aluminum and Aluminum-Magnesium Alloys

Abstract: The kind and amount of alloying elements strongly affects the formation of ultrafine-grained microstructures. Aluminum alloys with different amounts of the alloying element magnesium, and a commercially pure aluminum alloy, have been investigated in order to evaluate how the obtained microstructures will affect the mechanical properties. X-ray profile analysis has been used to determine grain size and dislocation density. With increasing amounts of alloying elements, a smaller grain size and a higher dislocation density after severe plastic deformation (SPD) are obtained, which lead to higher hardness and improved fatigue properties.

Effect of Grain Refinement on Jerky Flow in an Al-Mg-Sc Alloy

Abstract: The influence of microstructure on the manifestations of the Portevin–Le Chatelier (PLC) effect was studied in an Al-Mg-Sc alloy with unrecrystallized, partially recrystallized, and fully recrystallized grain structures. It was found that the extensive grain refinement promotes plastic instability: the temperature–strain rate domain of the PLC effect becomes wider and the critical strain for the onset of serrations decreases. Besides, the amplitude of regular stress serrations observed at room temperature and an intermediate strain rate increases several times, indicating a strong increase of the contribution of solute solution hardening to the overall strength. Moreover, the grain refinement affects the usual sequence of the characteristic types of stress serrations, which characterize the dynamical mechanisms governing a highly heterogeneous unstable plastic flow. Finally, it reduces the strain localization and surface roughness and diminishes the difference between the surface markings detected in the necked area and in the region of uniform elongation.