Room temperature stress-strain hysteresis in Ti2AlC revisited

Abstract

Room temperature cyclic compressive testing of high purity fine (FG) and coarse (CG) grained Ti 2 AlC 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 Ti 2 AlC can be divided in four stress regions with distinct underlying mechanisms: (a) Region I (FG: 0 to ≈ 175 MPa; CG: 0 to ≈ 100 MPa) characterized by a linear elastic behavior; (b) Region II (FG: from ≈ 175 to ≈ 350 MPa; CG from ≈100 to ≈ 200 MPa) in which stress strain hysteric behavior due to reversible dislocation flow in the soft grains; (c) Region III (FG: from ≈ 350 to ≈ 1100 MPa; CG from ≈200 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 ≈ 1100 MPa to failure, CG from ≈ 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.

In situ neutron diffraction evidence for fully reversible dislocation motion in highly textured polycrystalline Ti2AlC samples

“…These calculations -together with all the other evidence presented herein -should put to rest that DPs alone can explain the results such as those obtained herein as some have recently claimed [18]. Quite recently, Benitez et al have shown that after cyclically loading fine-and coarse-grained polycrystalline Ti 2 AlC samples in compression, a large concentration of LAKBs were nucleated throughout the microstructure, where none existed before and only after a permanent plastic deformation of less than 0.01% [28]! The average angle of these LAKBs was found to be %5°.…”

Characterization of Thermomechanical Behavior of Ti3SiC2 and Ti2AlC Ceramics Elaborated by Spark Plasma Sintering Using Ultrasonic Means

“…In case of Ti 2 AlC, the increased temperature influences significantly the number of recorded hits. Considering the work of Benitez on Ti 2 AlC material under cyclic compressive loading, one could easily relate the presence of impurities (TiAl x , Al 2 O 3 , TiC, 5 vol% in amount) with the possible occurrence of microcracking process due to elastic property mismatch between phases . The obvious fact of no detection of impurity in our Ti 2 AlC material, leads us to another hypothesis of interpretation concerning AE results.…”

“…In the literature, several works have already been conducted to study the mechanical properties of the MAX phases and to understand the involved deformation mechanisms . Standard stress‐strain curves exhibit a reversible nonlinear behavior during loading cycles . This fact leads to a significant deformation to rupture.…”

Non-classical crystallographic slip in a ternary carbide – Ti2AlC

“…In this process, Ti 2 AlC powder was first synthesized by pressure less sintering and then densified into bulk compact material by Spark Plasma Sintering, for more details, see ref. [25]. The fully dense Ti 2 AlC sample was annealed at 1400°C in a high-vacuum tube furnace under Ar atmosphere for 48 h to obtain coarsegrained microstructure.…”