2021 年 107 巻 9 号 p. 780-783
Dislocation strengthening is affected by not only dislocation density but also character and dispersion of dislocations. In terms of the effect of dislocation dispersion, strengthening behavior can be explained by applying a dispersion coefficient; δ (= n / ρ) in theoretical dislocation strengthening equation, here n and ρ are the number of dislocation colonies on a slip plane and dislocation density respectively. Dislocation pinning spacing is given as a function of n –value, so that the increment of strength Δσ can be theoretically estimated using the dispersion coefficient δ. In cold rolled ferritic steel (Fe-0.0056%C), the comparison of theoretical values with experimental data proved δ≒0.21 in the dislocation density range above 1×1014/m2. In addition, experimental results indicated that the screw component of dislocations decreases with an increase of dislocation density. With respect to the ability of dislocation strengthening, edge dislocation is about 1.4 times larger than screw dislocation. As a result, a linear Bailey-Hirsch relationship; Δσ[GPa]≒1.8×10−8ρ is realized due to the changes of dislocation character with an increase of dislocation density.
