Ti-44Al-6Nb-2Fe合金低温超塑性及高温拉伸组织演化

doi:10.11896/cldb.22090130

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Abstract In order to improve the hot deformation processing capability of high-Nb TiAl based alloys, this study used the Fe element to partly replace the Nb element in high-Nb TiAl based alloys to prepare the new-type high-Nb and Fe-contained Ti-44Al-6Nb-2Fe alloy. The alloy ingot was firstly isothermally package forged, and then the high-temperature tensile testing was carried out on this forged alloy at the initial strain rate of 1×10^-4 s^-1 and temperatures of 800—1 000 ℃, and the high-temperature tensile deformation behavior and microstructure evolution behavior of the alloy were studied. The results show that the alloy contains more B2 phases(30%—40%). With the increasing of temperature, the dynamic recrystallization effect increases, dislocation decreases, grain size increases, and aspect ratio of grains decreases, all of which correspond to the stress-strain state and enhancement of hot deformation processing capability of the alloy. When the tensile testing is at 800 ℃ and 850 ℃, B2 phase is a brittle phase, and the stress concentration in the regions of B2 phase and B2/γ phase interface leads to the formation of a large number of cracks and holes (14.5% cavity at 800 ℃), resulting in a low elongation (123.1% elongation at 800 ℃), even the early fracture, and the neck shrinkage is obvious. When the tensile testing is at 900 ℃, the strain-rate sensitive exponent m is 0.284, the elongation is significantly increased (163.0%), and the neck shrinkage still exists. When the tensile testing is at 950 ℃ and 1 000 ℃, B2 phase has transformed into a ‘soft’ phase that plays a good role in stress-strain coordination effect, and extensive grain boundary sliding between B2 phase and γ phase can be found. There are almost no cracks and holes in the microstructure, and the elongation increases sharply (307.9% at 950 ℃) without neck shrinkage. The alloy has superplasticity at 950 ℃ and 1 000 ℃, which belongs to low-temperature superplasticity for TiAl based alloys. The higher content of B2 phase and its excellent stress-strain coordination effect are the important reasons and characteristics for the alloy yielding the low-temperature superplasticity.

Key words： TiAl based alloy high-temperature tensile superplasticity microstructure evolution EBSD

Published: Online: 2024-01-16

CLC number:

TG146.2

Fund:Open Project of National Key Laboratory of Advanced Casting Technologies(CAT2023-008), Program for Liaoning Provincial Department of Education (LJKMZ20220464), Natural Science Foundation of Liaoning Province (2020-KF-14-03), and the State Key Laboratory of Light Alloy Casting Technology for High-end Equipment (LACT-009).

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	Articles by authors
	DONG Shulin
	QU Yingdong
	CHEN Ruirun
	GUO Jingjie
	WANG Qi
	LI Guanglong
	ZHANG Wei
	YU Bo

Cite this article:

DONG Shulin,QU Yingdong,CHEN Ruirun, et al. Low-temperature Superplasticity and High-temperature Tensile Microstructure Evolution of Ti-44Al-6Nb-2Fe Alloy[J]. Materials Reports, 2024, 38(1): 22090130-6.

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http://www.mater-rep.com/EN/10.11896/cldb.22090130 OR http://www.mater-rep.com/EN/Y2024/V38/I1/22090130

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