Hot deformation mechanism and microstructure evolution of an ultra-high nitrogen austenitic steel containing Nb and V

Abstract This article reports the microstructure evolution in TP347HFG austenitic steel during the aging process. The experiments were carried out at 700°C with different aging time from 500 to 3,650 h. The metallographic results show that the coherent twin and incoherent twin are existed in the original TP347HFG grains, while they gradually vanished with the increase of the aging time. After aging for 500 h, a lot of fine, dispersed particles precipitated from the matrix, but they disappeared after aging for 1,500 h. When the aging time extend to 3,650 h, the precipitates appeared apparently coarse in TP347HFG steel, which include the M23C6 and σ phase; besides, the micro-hardness of TP347HFG also changes during the aging, which was closely related to the effect of dispersion strengthening and solution strengthening. The results of the nonlinear ultrasonic measurement reveal that the β′ of TP347HFG steel was also changed with the aging time. It first increased at 0–500 h, then reduced later, and increased finally at 1,500–3,650 h. The variation of β′ in TP347HFG was influenced by a combined effect of the twin microstructure and the precipitate phase, which indicate that the nonlinear ultrasonic technique can be utilized to characterize the microstructure evolution in TP347HFG.

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Hot deformation behavior and related microstructure evolution in Au−Sn eutectic multilayers

Transactions of Nonferrous Metals Society of China ◽

10.1016/s1003-6326(21)65609-1 ◽

2021 ◽

Vol 31 (6) ◽

pp. 1700-1716

Author(s):

Yong MAO ◽

Dan-li ZHU ◽

Jun-jie HE ◽

Chao DENG ◽

Ying-jie SUN ◽

...

Keyword(s):

Microstructure Evolution ◽

Hot Deformation ◽

Deformation Behavior ◽

Hot Deformation Behavior

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Hot Deformation Behavior and Processing Maps of a New Ti-6Al-2Nb-2Zr-0.4B Titanium Alloy

Materials ◽

10.3390/ma14092456 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2456

Author(s):

Zhijun Yang ◽

Weixin Yu ◽

Shaoting Lang ◽

Junyi Wei ◽

Guanglong Wang ◽

...

Keyword(s):

Titanium Alloy ◽

Flow Stress ◽

Constitutive Equation ◽

Deformation Mechanism ◽

Power Dissipation ◽

Hot Deformation ◽

Dissipation Rate ◽

Dynamic Recovery ◽

Processing Maps ◽

Temperature Range

The hot deformation behaviors of a new Ti-6Al-2Nb-2Zr-0.4B titanium alloy in the strain rate range 0.01–10.0 s−1 and temperature range 850–1060 °C were evaluated using hot compressing testing on a Gleeble-3800 simulator at 60% of deformation degree. The flow stress characteristics of the alloy were analyzed according to the true stress–strain curve. The constitutive equation was established to describe the change of deformation temperature and flow stress with strain rate. The thermal deformation activation energy Q was equal to 551.7 kJ/mol. The constitutive equation was ε ˙=e54.41[sinh (0.01σ)]2.35exp(−551.7/RT). On the basis of the dynamic material model and the instability criterion, the processing maps were established at the strain of 0.5. The experimental results revealed that in the (α + β) region deformation, the power dissipation rate reached 53% in the range of 0.01–0.05 s−1 and temperature range of 920–980 °C, and the deformation mechanism was dynamic recovery. In the β region deformation, the power dissipation rate reached 48% in the range of 0.01–0.1 s−1 and temperature range of 1010–1040 °C, and the deformation mechanism involved dynamic recovery and dynamic recrystallization.

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