Room temperature stress-strain hysteresis in Ti2AlC revisited

Room temperature cyclic compressive testing of high purity fine (FG) and coarse (CG) grained Ti2AlC were carried out in combination with Resonant Ultrasound Spectroscopy (RUS) tests and post mortem Electron-backscatter Diffraction (EBSD). The results show that the room temperature mechanical response of Ti2AlC can be divided in four stress regions with distinct underlying mechanisms: (a) Region I (FG: 0 to approximate to 175 MPa; CG: 0 to approximate to 100 MPa) characterized by a linear elastic behavior; (b) Region II (FG: from approximate to 175 to approximate to 350 MPa; CG from approximate to 100 to approximate to 200 MPa) in which stress strain hysteric behavior due to reversible dislocation flow in the soft grains; (c) Region III (FG: from approximate to 350 to approximate to 1100 MPa; CG from approximate to 200 to approximate to 650 MPa) accumulation of dislocation walls (DWs) results in cyclic hardening and contribute to larger hysteretic loops and thus a larger energy dissipation per loading cycle than in Region II; (d) Region IV (FG: from approximate to 1100 MPa to failure, CG from approximate to 600 MPa to failure) characterized by the occurrence of microcracking that, in addition to the other aforementioned deformation mechanisms, contributes to the energy dissipated in each loading cycle. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.