Effect of laser beam welding on fracture toughness of a Ti-6.5Al-2Zr-1Mo-1V alloy sheet
Investigation of fracture toughness on Ti-6.5Al-2Zr-1Mo-1V alloy thin sheet and its laser-welded joints has been carried out. In the test compact tension (CT) specimens and single specimen technology were used. In addition, hardness distribution and microstructure of the welded joints were examined. Fracture test indicates that brittle unstable fracture occurs after slow crack propagation for all the specimens, except that one heat affected zone (HAZ) specimen is brittle crack initiation. It is found that rolling directions have no obvious effect on fracture toughness of base metal. Moreover, fracture toughness of weld metal is obviously decreased in comparison with base metal whatever in as-welded condition or in stress relief condition. Post-weld heat treatment (PWHT) leads to fracture toughness of the welds further decreasing. Fractography observation shows that the fracture mode is predominantly dimpled in base metal. However, there exists intergranular fracture in the weld metal. Thus, the transition of fracture mode from both base metal and HAZ to weld metal may lead to dramatic decrease in fracture toughness. Microstructure examination reveals that the microstructure of weld metal consists of large grains with fine acicular structure. The formation of fine α acicular structure is due to rapid cooling during laser welding. After PWHT, the acicular structure is coarsened.
KeywordsWelding Fracture Toughness Base Metal Weld Metal Fusion Zone
The authors would like to express their thanks to the financial support from the State Defence Key Laboratory For High Energy Density Beam Processing Technology.
- 1.Khorev MA (1983) Automat Wel 7:21 (in Russian)Google Scholar
- 2.Yao W, Gong SL, Chen L (2003) Welding 7:21 (in Chinese)Google Scholar
- 3.Gong SL, Tang Y, Du X, Ba RZ (2002) Welding 10:32 (in Chinese)Google Scholar
- 4.Wang ZM, Hong XF, Cao WJ (2005) Aerosp Manufact Technol 1:4 (in Chinese)Google Scholar
- 5.Xiong LT, Zhou ZG, Dong ZG (2006) Trans China Weld Inst 27:49 (in Chinese)Google Scholar
- 6.Du X, Liu LM, Song G, Wang M, Yang L (2005) Trans China Weld Inst 26:45 (in Chinese)Google Scholar
- 7.Keshava MK, Sundaresan S (1997) Weld J 76:81sGoogle Scholar
- 12.Torsten F, Santos JF, Kocak M, Penasa M (1998) In: ASM Proceedings of the International conference: Trends in Welding Research, Pine Mountain, GA, ASM International and American Welding Society, 887Google Scholar
- 13.National Standards (2001) GB 3076-82 Standard test method for tensile testing of metallic thin sheet, China Standards Publisher, BeijingGoogle Scholar
- 14.British Standard (1997) BS 7448, Method for determination of K 1c, critical CTOD and critical J value of welds in metallic materials, LondonGoogle Scholar