Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 852, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2022.143695
Keywords
TiAl alloys; Hot deformation; Flow behavior; Microstructure evolution; Constitutive modelling; Numerical simulation
Categories
Funding
- National Natural Science Foundation of China [51905233, 5210130372]
- Natural Science Basic Research Plan in Shaanxi Province [2022JM-179]
- Postdoctoral Science Foundation of Jiangsu Province [2019K133]
- Jiangsu ShuangChuang project
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This study investigated the deformation pattern and mechanical response of a Ti-43.5Al-8Nb-0.2W-0.2B alloy with refined fully lamellar microstructure. The results showed that the plastic anisotropy of the lamellar colonies led to bending deformation, slow recrystallization kinetics, and crystalline rotation. Numerical simulation demonstrated that the mechanical response of the colonies depended on the prior orientation, with continuous flow hardening observed at certain interfaces.
In comparison with ordinary alloys, it is well-known that the high temperature flow curves of lamellar TiAl alloys generally exhibit pronounced flow softening and sharp stress peak. In order to clarify the origin of the abnormal flow behavior, in this study a Ti-43.5Al-8Nb-0.2W-0.2B alloy with refined fully lamellar microstructure was isothermally compressed at ( alpha+gamma) phase field. The deformation pattern as well as the mechanical response was studied by means of experimental analysis and finite-element modelling. Microstructural observations revealed that the lamellar colony exhibited significantly plastic anisotropy due to the preferential activity of the longitudinal slip systems with the slip plane/direction parallel to the lamellar interface. Consequently, lamellar kinking/bending predominated the deformation, and the colonies showed rather retarded recrystallization kinetics as well as significant crystalline rotation toward the hard orientation. The numerical simulation demonstrated that the mechanical response of individual lamellar colonies was strongly dependent on the prior orientation. When the interface aligned in about 30-60 degrees with respect to the compression axis, the colony exhibited continuous flow hardening. Otherwise evident flow softening occurred at the beginning of straining. Analysis of the deformation pattern revealed that the mechanical response of the colony was attributed to the peculiar crystalline rotation pathway of the lamellae, which was fundamentally determined by the preferential activity of the longitudinal slip. The proposed numerical model reproduced the experimental phenomena quite well, and provided insights into the flow softening mechanism of lamellar TiAl alloys.
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