Grain boundary diffusion of 181W in Fe — Cr ferritic alloys

The Grain-Boundary Diffusion of Zn in α-Fe

“…[16] Also, the activation energy for the grain-boundary diffusion of W in ferritic Fe-8 wt.%Cr alloys ranges from 192 to 252 kJ depending on the carbon content. [17] It appears that the grain-boundary diffusion of Zn in Fe is consistent with normal grain-boundary diffusion. The experimental results shown in Fig.…”

Evolution of Laves-Phase Particles in a Low Carbon 9%Cr Martensitic Steel during Creep at 650°C

“…2, with the different growth rates can be distinguished on the plot with an inflection point at 1500 hours as indicated by the dotted line. Generally, the kinetics of particle growth can be described by the following empirical function: R = Kτ Ν , were R is the average size of particles, τ is the time of aging, K and N are constants [20][21][22]. It Advanced Materials Research Vol.…”

“…were R -particle size at the time, R 0 -initial particle size, K -constant of growth rate, τ -time. The rate constant is determined by the following equation [20][21][22][23]: (2) where is the energy of matrix/particle interface (the common value of 1 J/m 2 is used). The equillibrium concentration of tungsten in matrix = 7.5 × 10 2 mole/m 3 , the molar volume of Fe 2 W Laves-phase Ω = 7.9 × 10 -6 м 3 /mole, and the volume fraction of precipitates = 0.017 were calculated using ThermoCalc.…”

Coarsening of Laves phase and creep behaviour of a Re-containing 10% Cr-3% Co-3% W steel

“…The Q values for nucleation are calculated as 116 and 138 kJ mol − 1 for creep and long-term ageing, respectively, taken D = 1.59 × 10 − 23 m 3 s − 1 as the grain boundary diffusion coefficient, for 923 K [56]. The D values of W in ferromagnetic α-Fe (A c2 is ~1053 K for this type of steels [57]) reported in works [58][59][60] are distinctly different. The values of activation energy are less than half of the activation energy for volume diffusion of W (Q F = 245 kJ mol − 1 ) in ferromagnetic state [58][59][60].…”

“…The values of activation energy are less than half of the activation energy for volume diffusion of W (Q F = 245 kJ mol − 1 ) in ferromagnetic state [58][59][60]. We may assume that nucleation process is controlled by grain boundary or pipe diffusion of W solute since their activation energies are usually the same despite the fact that Cermak et al [57] reported a value of 195 kJ mol − 1 as activation energy for grain boundary diffusion of W solutes in α-ferrite. For the Co-modified P911-type steel, the activation energy for growth of the Laves phase particles is 60 kJ mol − 1 [32], which is also less than the activation energy for volume diffusion of tungsten [58][59][60].…”