1 Shenyang National Laboratory of Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
2 AVIC Shenyang Aircraft Corporation, Shenyang 110034, China
Cite this article:
Yongkui LI, Chunyi QUAN, Shanping LU, Qingyang JIAO, Shijian LI, Zhonghai SUN. STUDY ON SHAPE CORRECTION OF THE THIN PLATE OF TA15 TITANIUM ALLOY BY POST WELD HEAT TREATMENT. Acta Metall Sin, 2016, 52(3): 281-288.
Weld deformation of the thin-wall weldment used in fighter aircraft not only hinders its subsequent procedure of fabrication and assembling, but also reduces its fatigue strength. As a result, weld deformation shortens its service life essentially. Dustpan deformation is always produced in the thin-wall weldment after multiple-pass weld. In this work, combining with the experiment, the finite element method was adopted to analysis the deformation of the thin-wall weldment by multiple-pass weld and its shape correction by post weld heat treatment. For obtaining the fundamental properties such as thermal parameters and mechanical parameters of TA15 titanium alloy, a series of experiments were conducted at room temperature and high temperatures. Additionally, creep behaviors of TA15 titanium alloy were studied at the temperatures of 500, 550, 600, 650, 700 and 750 ℃, and the parameters of creep constitutive equations of the alloy were obtained with considering the analysis of post weld heat treatment. A thermal coupled temperature-displacement analysis for welding and post weld heat treatment was performed on a three dimensional shell model of protective grille. Experiments of multiple-pass weld and post weld heat treatment were used to testify the reliability of the finite element model of welding and post weld heat treatment. With using the reliable finite element model, the parameters of heat treatment were studied. The study indicates that, the fabrication on the crossing of structure section and fillet after fillet-wallboard weld leads the compression deformation release along the fillet, after that, the shrinkage distortion produced during spot welding of fillet-structural section mainly contributes the large dustpan deformation of the thin-wall weldment; increasing temperatures, enlarging loads and prolonging the hold time can improve the shape correction of the thin-wall weldment during post weld heat treatment, hence the guide maps of the post weld heat treatment for shape correction of the thin-wall weldment under 700 and 750 ℃ are worked out.
Fig.1 Thermo-physical parameters of TA15 titanium alloy
Fig.2 True stress-plastic strain curves of TA15 titanium alloy with temperature
Fig.3 Creep behaviors of TA15 titanium alloy at 700 ℃ (a) and 750 ℃ (b)
Temperature / ℃
A / (s-1MPa-n)
n
600
6.27×10-15
3.6
650
3.07×10-11
2.4
700
3.24×10-10
2.3
750
1.43×10-9
2.3
Table 1 Creep properties of TA15 titaniun alloy under elevated temperatures
Fig.4 Creep constitutive relations of TA15 titanium alloy at elevated temperatures
Fig.5 Sketch map of the thin-wall weldment
Location
Current A
Voltage V
Welding rate (cmmin-1)
Cooling condition
Fillet-wallboard
310~330
9~10
8~10
Copper billet+Ar
Structural section-wallboard
310~330
9~10
8~10
Ar
Fillet-structural section
Spot welding
Spot welding
Spot welding
Ar
Table 2 Welding parameters of the protective grille
Fig.6 Welding deformation of the thin-wall weldment by simulation
Fig.7 Displacement along paths of the thin-wall weldment after weld (1700 mm in the figure denotes the cross section in the thin-wall closed to the cylinder, while 0 mm presents the remote crossing section to the cylinder)
Fig.8 Simulation result of shape correction of the thin-wall weldment by heat treatment
Fig.9 Effects of the holding time on shape correction of the thin-wall weldment by heat treatment under 600 ℃ (a), 650 ℃ (b), 700 ℃ (c) and 750 ℃ (d) (Shape corrections of the grille by heat treatment are desired when the flatness is in the shadow region under the temperatures of 600, 650, 700 and 750 ℃)
Fig.10 Effects of the clamp thickness on shape correction of the thin-wall weldment by heat treatment under 750 ℃
Fig.11 Effects of temperatures on shape correction of the thin-wall weldment by heat treatment with holding 2 h
Fig 12 Maps of post weld heat treatment for the thin-wall weldment of TA15 titanium alloy under 700 ℃ (a) and 750 ℃ (b)
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