2017 年 57 巻 3 号 p. 573-580
Mechanical properties of ferrite/cementite lamellar structure model in pearlite steel with the Pitsch-Petch orientation relationship are examined by a strain gradient crystal plasticity analysis. Dislocations’ behavior in the lamellar structure is especially considered in the analysis and characteristic lengths of the structure used in its constitutive equations are approximately determined for each slip system. From the analysis results for different lamellar thicknesses, a scale effect on the yield stress of the pearlite model is smaller than that in case of uniform estimation of the characteristic length by the lamellar thickness because of a reduction of the Orowan stress. The yield stress shows better agreement with an experimental result. On the other hands, a scale effect on the strain hardening rate is larger than that of the uniformly estimation. This is attributed to obvious change of active slip systems in the ferrite layer associated with the thickness. It is found that while slip systems with the largest Schmid factor act in case of large thickness, slip systems which have small critical resolved shear stress act in case of small thickness due to the increase of slip anisotropy. And the change of active slip systems arises large shear incompatibility in each layer and makes the stress fields in the layer non-uniform for the model with Pitsch-Petch relationship.
