Microstructural Parameters in Large Strain Deformed Ni Polycrystals as Investigated by Synchrotron Radiation

Effect of thermal treatment on microstructure in high pressure torsion (HPT) deformed nickel

“…A lower strain range as shown in Fig. 3(b) of [19] includes the formation and transformation of a dislocation cell structure with tilt character being the pre-stage of a subgrain structure. The continuation of this process can only be provided by methods of severe plastic deformation achieving significantly higher strains.…”

“…2 and exhibits the same behavior as the dislocation density. The initial value of the long range internal stresses in the as deformed state is comparable or even lower than the results from cold rolled nickel [19], what seems to be strange as the strain is much higher here. A lower strain range as shown in Fig.…”

Plastic deformation of nickel under high hydrostatic pressure

“…First it has to be noted that both the measured values c v exp and the calculated ones c v calc are far higher than the value of vacancy concentration in thermal equilibrium under atmospheric pressure. In Table 1, the value of H m (0) = 0.62 eV was taken for the sake of consistency between the concentration c v exp experimentally determined from residual resistivity data [14,15] and the concentration c v calc calculated from the results of the τ(γ) and ρ(γ) fits for atmospheric pressure 0.1 MPa [14]. The result of c v calc for 1.3 GPa is acceptable, but these for the higher pressures are not acceptable as the Table 2 Same data as given in Table 1, but resulting from fits of τ(γ) with a vacancy migration enthalpy H m (p = 0) = 0.2 eV.…”

“…increases with increasing hydrostatic pressure p. This has the consequence that the diffusion of vacancies will be restricted leading to even restricted annihilation (i) of vacancies at sinks; (ii) of edge dislocations with less climb because of less mobile vacancies [2,7]. This modification allows calculating the concentrations of deformation induced vacancies for all applied hydrostatic pressures from the parameter C 4 of the τ(γ) and ρ(γ) fits and the comparison with the vacancy concentrations determined by experiment (i.e., electrical resistivity measurements [15,16]). …”

Formation of nano-laminated structure in nickel by means of surface mechanical grinding treatment

“…In the present case, a strain gradient of 0.26-0.63 lm À1 corresponds to a q G value of 4.2-10 Â 10 15 m À2 , which is much higher than the steady-state dislocation density during low rate deformation ($2 Â 10 15 m À2 ) [37]. Besides, GNDs may also influence the accumulation, mutual annihilation and trapping of statistically stored dislocations.…”