An in-situ neutron diffraction study of a multi-phase transformation and twinning-induced plasticity steel during cyclic loading

In-situ neutron diffraction during cyclic tension-compression loading (similar to+3.5% to -2.8%) of a 17Mn-3Al-2Si-1Ni-0.06C steel that exhibits concurrent transformation and twinning -induced plasticity effects indicated a significant contribution of intragranular back stresses to the observed Bauschinger effect. Rietveld analysis revealed a higher rate of martensitic transformation during tension compared to compression. Throughout cycling, alpha'-martensite exhibited the highest phase strains such that it bears an increasing portion of the macroscopic load as its weight fraction evolves. On the other hand, the epsilon-martensite strain remained compressive as it accommodated most of the internal strains caused by the shape misfit associated with the gamma ->epsilon and/or epsilon ->alpha' transformations. (C) 2015 AIP Publishing LLC.