Adiabatic temperature increase associated with deformation twinning and dislocation plasticity

We studied local deformation and temperature effects associated with mechanical twinning in Fe-3 wt.% Si at room temperature. During tensile testing, two large stress drops occurred. They were accompanied by local strain and temperature bursts, which we mapped via simultaneous displacement and temperature field characterization. To identify the microstructural origin of these phenomena, we performed high resolution electron backscatter scanning diffraction and electron channeling contrast imaging measurements. The microstructure at the positions where strong adiabatic heating occurred was characterized by the formation of primary twins and high dislocation activity within a range of about 10 mu m around the twin matrix interface. We suggest that the local temperature and strain jumps result from the formation and dissipative motion of lattice dislocations that accommodate twinning. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.