1 School of Mechanical Engineering and Automation, Beihang University, Beijing 100191 2 Beijing Aeronautical Manufacturing Technology Research Institute, Beijing 100024
Cite this article:
Yunhua DENG,Qiao GUAN,Jun TAO,Bing WU,Xichang WANG. EFFECT OF ELECTRON BEAM POWER ON TC4 ALLOY RIGID RESTRAINT THERMAL SELF-COMPRESSING BONDING, MICRO- STRUCTURE AND MECHANICAL PROPERTIES OF JOINTS. Acta Metall Sin, 2015, 51(9): 1111-1120.
Rigid restraint thermal self-compressing bonding is a new solid-state bonding process. During the process, localized non-melted heating method is employed to heat the butted interface of the rigid restrained plates to be bonded. Under the localized heating, materials close to the butted interface are expanded. However, due to the existence of surrounding cool metals and rigid restraints, the expansion of the high temperature materials is restrained and thus, a compressive pressure is developed which compresses the high temperature metals near the bond interface and facilitates the atom diffusion between butt-weld specimens to produce a permanent solid-state joint. Utilizing the localized stress-strain field to accomplish atomic bonding, this process can avoid the use of external forces on which diffusion bonding and other solid-state bonding methods rely. Previous study has proven the feasibility of this process to join titanium alloys. In present work, the effect of beam power on bond interface, microstructure and mechanical properties of the TC4 joints bonded at different beam powers were analyzed through the OM observation, EBSD analysis, mechanical property test and fracture morphology analysis. Meanwhile, in order to reveal the mechanism about the effect of beam power on bond interface, the experiment study on microstructure and mechanical property and finite element analysis on present bonding were conducted to investigate the effect of beam power on the thermal stress-strain process during bonding. The results show that with the increase of beam power, the heating temperature, dwell time over high temperature, volume of materials with high temperature and the compressive plastic strain increase which promote the atom diffusion and thus bond quality of the interface is improved. At low beam power, the microstructure of the joints is homogeneous, while coarse grain with acicular a phase forms in the joint when the beam power is high. Mechanical properties of the joint are dependent on bond rate and microstructure. When the beam power is lower or higher, the compressive mechanical properties of the joints are poor because of the poor bonding quality of the interface or the coarse microstructure developed in the joint. Good comprehensive mechanical properties are obtained at the beam power of 330 W.
Fig.1 Schematic of rigid restraint thermal self-compressing for TC4 alloy (F—thermal compressive pressure)
Specimen
UbkV
IbmA
P W
tHs
1
150
1.8
270
150
2
150
2.2
330
150
3
150
5.2
780
150
Table 1 Parameters of rigid restraint thermal self-compressing bonding
Fig.2 Schematic of dimensions of tensile specimen (unit: mm)
Fig.3 Bond interfaces of TC4 alloy joints by rigid restraint thermal self-compressing bonding at beam powers of 270 W (a), 330 W (b) and 780 W (c)
Fig.4 Microstructure of TC4 alloy base metal
Fig.5 Grain orientation maps of TC4 alloy base metal (a) and joints at beam powers of 330 W (b) and 780 W (c) (Insets show the corresponding pole figures)
Fig.6 Misorientation angle distributions of a phase in TC4 alloy base metal (a) and the joints at beam powers of 330 W (b) and 780 W (c)
Fig.7 Fracture locations (insets) and morphologies of TC4 alloy joints at beam powers of 270 W (a), 330 W (b) and 780 W (c)
Specimen
P W
sbMPa
s0.2MPa
d%
Fracture location
Base metal
-
999.3
944.7
17.4
-
1
270
405.1
-
≈0
Interface
2
330
1029.0
964.3
16.2
Base metal
3
780
997.2
901.5
3.5
Heated zone
Table 2 Mechanical properties of TC4 alloy base metal and joints bonded at different beam powers
Fig.8 Mesh generation near the bond interface (P1—central point of bond line on top surface, P2—middle point of bond interface, P3—central point of bond line on low surface)
Fig.9 Illustration of elongated Gaussian surface heat source (l—length of elongated Gaussian surface heat source)
Fig.10 Comparison between numerical and experimental results of thermal cycles (a) and residual stress distributions (b) (sx—longitudinal residual stress along x direction, sy—transversal residual stress along y direction)
Fig.11 Thermal cycles of points P1 (a), P2 (b) and P3 (c) shown in Fig.8 during TC4 alloy bonding at different beam powers
Fig.12 Temperature distributions on middle cross-section of TC4 alloy during bonding at different beam powers
Fig.13 Transversal stress and strain evolutions of middle point of bond interface (P2) during bonding at beam powers of 270 W (a), 330 W (b) and 780 W (c) for TC4 alloy
Fig.14 Temperature distributions of different beam powers at heating time about 10 s for TC4 alloy
Fig.15 Temperature distributions when the compressive stresses reaching the peak values at different beam powers (t—time)
[1]
Kou S. Welding Metallurgy. 2nd Ed., New Jersey: John Wiley & Sons, 2003: 170
[2]
Kou S. JOM, 2003; 55(6): 37
[3]
Liu J, Gao X L, Zhang L J, Zhang J X. J Mater Eng Perform, 2014; 20: 319
[4]
Milella P P. Fatigue and Corrosion in Metals. Milan: Springer-Verlag, 2013: 625
[5]
Deng Y H, Guan Q, Wu B, Wang X C, Tao J. Mater Lett, 2014; 129: 43
[6]
Deng Y H, Guan Q. Mater Lett, 2015; 146: 1
[7]
China Aeronautical Materials Handbook Edit Committee. China Aeronautical Materials Handbook. Vol.4, Beijing: China Standard Publishing Company, 2002: 9 (中国航空材料手册编委会. 航空材料手册. 第四卷, 北京: 中国标准出版社, 2002: 9)
[8]
Каракоэов Э С,translated by Zhai S F. Diffusion Bonding of Titanium Alloy. Beijing: National Defense Industry Press, 1986: 36 (Каракоэов Э С著,翟书汾译. 钛合金的扩散焊接. 北京: 国防工业出版社, 1986: 36)
[9]
Wu G Q, Li Z F, Luo G X, Li H Y, Huang Z. Mater Sci Eng, 2007; A452-453: 529
[10]
Liu H, Nakata K, Zhang J X, Yamamoto N, Liao J. Mater Charact, 2012; 65: 1
[11]
Mills K C. Recommended Values of Thermophysical Properties for Selected Commercial Alloys. London: Woodhead Publishing Ltd, 2002: 217
[12]
Lacki P, Adamus K. Comput Struct, 2011; 89: 977
[13]
Luo Y, Liu J H, Ye H. Vacuum, 2010; 84: 857
[14]
Rouquette S, Guo J, Le P. Int J Therm Sci, 2007; 46: 128
[15]
Liu C, Wu B, Zhang J X. Metall Mater Trans, 2010; 41B: 1129
[16]
Lacki P, Adamus K, Wieczorek P. Comput Mater Sci, 2014; 94: 17
[17]
Cai Y. Master Thesis, Nanjing University of Aeronautics and Astronautics, 2009 (蔡 云. 南京航空航天大学硕士学位论文, 2009)
[18]
Guan Q, Cao Y. Weld World, 1999; 43(1): 14
[19]
Li J. PhD Dissertation, Beijing University of Technology, 2004 (李 菊. 北京工业大学博士学位论文, 2004)
[20]
Ma R F, Li M Q, Li H. Sci China Technol Sci, 2012; 55: 2420
[21]
Shen J J. Master Thesis, Harbin Institute of Technology, 2007 (沈俊军. 哈尔滨工业大学硕士学位论文, 2007)
[22]
Hill A, Wallach E R. Acta Meter, 1989; 19: 2425
[23]
Orhan N, Aksoy M, Eroglu M. Mater Sci Eng, 1999; A271: 458
[24]
Mehrer H.Diffusion in Solids: Fundamentals, Methods, Materials, Diffusion-Controlled Process. Berlin: Springer and Verlag, 2007: 310
[25]
Zhang Z,Wang Q J,Mo W. Metallurgy and Heat Treatment of Titanium. Beijing: Metallurgical Industry Press, 2009: 87 (张 翥,王群骄,莫 畏. 钛的金属学和热处理. 北京: 冶金工业出版社, 2009: 87)
