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Materials 2017, 10(12), 1437; https://doi.org/10.3390/ma10121437

Hot Deformation Behavior and Pulse Current Auxiliary Isothermal Forging of Hot Pressing Sintering TiAl Based Alloys

1
School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
2
National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, China
*
Authors to whom correspondence should be addressed.
Received: 20 November 2017 / Revised: 9 December 2017 / Accepted: 11 December 2017 / Published: 16 December 2017
(This article belongs to the Section Structure Analysis and Characterization)
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Abstract

This paper focuses on the fabrication of as-forged Ti46.5Al2Cr1.8Nb-(W, B) alloy via pulse current auxiliary isothermal forging (PCIF). The starting material composed of near gamma (NG) microstructure was fabricated by adopting pre-alloyed powders via hot pressing sintering (HPS) at 1300 °C. Isothermal compression tests were conducted at a strain rate range of 0.001–0.1 s−1 and a temperature range of 1125–1275 °C to establish the constitutive model and processing map. The optimal hot deformation parameters were successfully determined (in a strain rate range of 10−3–2.5 × 10−3 s−1 and temperature range of 1130–1180 °C) based on the hot processing map and microstructure observation. Accordingly, an as-forged TiAl based alloy without cracks was successfully fabricated by PCIF processing at 1175 °C with a nominal strain rate of 10−3 s−1. Microstructure observation indicated that complete dynamic recrystallization (DRX) and phase transformation of γ→α2 occurred during the PCIF process. The elongation of as-forged alloy was 136%, possessing a good secondary hot workability, while the sintered alloy was only 66% when tested at 900 °C with a strain rate of 2 × 10−4 s−1. View Full-Text
Keywords: TiAl based alloys; hot pressing sintering; hot deformation behavior; microstructure evolution; pulse current auxiliary isothermal forging TiAl based alloys; hot pressing sintering; hot deformation behavior; microstructure evolution; pulse current auxiliary isothermal forging
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Shi, C.; Jiang, S.; Zhang, K. Hot Deformation Behavior and Pulse Current Auxiliary Isothermal Forging of Hot Pressing Sintering TiAl Based Alloys. Materials 2017, 10, 1437.

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