Internal Stress and Elastic Strain Energy in Pearlite and Their Accommodation by Misfit Dislocations

摘要

Internal stress and elastic strain energy in pearlite caused by misfit between ferrite and lamellar cement-ite were theoretically analyzed based on micromechanics while taking into account an accommodation mechanism of the misfit strain between ferrite and cementite on pearlitic transformation. Two-dimensional large deformation analysis reveals that the Pitsch-Petch orientation relationship is most appropriate among already reported crystal orientation relationships under the condition that the interface contains a lattice invariant direction. However, the micromechanics analysis using a periodic function proves that the misfit strain generates very large elastic strain energy in pearlite even when the Pitsch-Petch orientation relationship is satisfied, which is almost comparable to the chemical driving force for pearlitic transformation. Assuming that an interval of misfit dislocations dynamically introduced at ferrite/cementite interface upon pearlitic transformation depends on the growth rate of pearlite, the total elastic strain energy reduces more effectively as the growth rate becomes lower. As a result, the elastic strain energy in pearlite changes widely depending on interlamellar spacing.