Kinetics of cyclically-induced mechanical twinning in γ-TiAl unveiled by a combination of acoustic emission, neutron diffraction and electron microscopy

0542932 - ÚFM 2022 RIV GB eng J - Journal Article
Vinogradov, A. - Heczko, Milan - Mazánová, Veronika - Linderov, M. - Kruml, Tomáš
Kinetics of cyclically-induced mechanical twinning in γ-TiAl unveiled by a combination of acoustic emission, neutron diffraction and electron microscopy.
Acta Materialia. Roč. 212, JUN (2021), č. článku 116921. ISSN 1359-6454. E-ISSN 1873-2453
R&D Projects: GA MŠMT(CZ) LQ1601; GA MŠMT(CZ) EF16_025/0007304
Institutional support: RVO:68081723
Keywords : Acoustic emission * Cyclic deformation * Dislocation slip * Microscopy * Neutron diffraction * TiAl alloy * Twinning
OECD category: Materials engineering
Impact factor: 9.209, year: 2021
Method of publishing: Limited access
https://www.sciencedirect.com/science/article/pii/S1359645421003013?via%3Dihub

The cyclic response and the microstructure evolution of the near γ-TiAl alloy are investigated by a blend of contemporary experimental techniques centred around in-situ acoustic emission (AE) measurements reflecting the cyclically-induced structural changes in the real-time scale. TEM and SEM – ECCI/EBSD examinations provided an adequate qualitative description of microstructural features associated with populations of dislocations and mechanical twins evolving concurrently in the course of cyclic deformation. Since the TEM offers only local and post-mortem information, the in-situ neutron diffraction technique scanning a large part of the gauge length was employed to characterise the lattice strain distributions with cycling. The volume fraction of twins as a function of loading cycles was obtained after loading or unloading half-cycles. The processes controlling the cyclic strain hardening during each deformation cycle were assessed by (i) the statistical analysis of the shape of the hysteresis loop aiming at the characterisation of distribution internal stress barriers for deformation mechanisms involved and (ii) the spectral and statistical analysis of AE data providing information on the kinetics of these mechanisms. Each of the used experimental methods brings its own set of advantages and limitations in terms of characterisation and interpretation. Their unique combination ensures a host of benefits that promote a comprehensive understanding of primary deformation mechanisms - deformation twinning, dislocation slip and detwinning. It is shown that the cyclic mechanical behaviour of the TiAl alloy can be comprehensively explained by the interplay between these mechanisms co-operating during each loading cycle. This interplay governs the behaviour of underlying mechanisms in the early stages of the fatigue damage evolution and likely determines the overall fatigue response of near γ-TiAl alloy at room temperature. © 2021 Acta Materialia Inc.
Permanent Link: http://hdl.handle.net/11104/0320812