Load transfer and strain gradients in pearlite investigated by means of in-situ neutron diffraction

In-situ neutron diffraction experiments have been performed during tensile testing of undeformed and cold rolled pearlite. The microstructure of the samples varied from spheroidised cementite to randomly oriented lamellae to lamellae aligned with the loading direction. Both the ferrite lattice strain and diffraction peak width have been analysed. Conclusions were drawn regarding the influence of cementite morphology on load transfer from ferrite to cementite. The ferrite lattice strain was found to decrease after yielding in a sample with aligned lamellae, whereas an increasing ferrite lattice strain would be expected. This might be explained based on the non-ideal nature of the lamellar microstructure. Upon unloading of the material, the diffraction peak width decreases, which may be attributed to strain gradients in the deformed pearlite.