Mechanical properties and microstructural study of homogeneous and heterogeneous laser welds in α, β, and α + β titanium alloys
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Heterogeneous welding has been investigated for three different couples of titanium alloys: α/α + β, α/β, and α + β/β. Plates of 100 × 60 mm and 1.6 or 1.8 mm thick were welded with a Yb:YAG laser. Tensile tests show that the resistance of the heterogeneous welded specimens was generally controlled by those of the weakest material except for the α + β/β where the ultimate tensile strength was approximately equal to the average value of both materials. In every case, the elongation of the welded sample was found to be smaller than that of the base metals. The rupture generally took place outside the weld metal and was found to be most of the time located in the alloy having the lowest mechanical properties. Nevertheless, a few large-size porosities detected by tomography in the α + β/β couple could explain why rupture for these samples occurred in the weld bead. For each couple, the porosities were situated at the board between the heat-affected zone and the molten zone. EBSD maps and EDX enabled the observation of different microstructures, which could be correlated to the heterogeneous composition and diffusion into the melted bath. When the stable microstructure of one of the couple alloys is the β phase, the molten zone of the bead consists of an alternative disposition of thin layers made of large equiaxed β grains and nano-martensite α′. That is explained by the weak diffusion of the alloying elements.
KeywordsTitanium alloys Laser welding Heterogeneous joints Microstructure Mechanical properties
The authors would like to thank Mélanie Duband (LICB) and Patrick Moll (LEM3) for their help during the experiments.
This research has been funded by the Laboratory of Excellence for Design of Alloy Metals for Low-mass Structures (‘DAMAS’ Labex).
- 8.Ferdinand C (2005) Mise en oeuvre et caracterisation d'assemblages soudés par procédés TIG et laser de tôles d'alliages de titane refractaire (in French), PhD thesis, INPT, FranceGoogle Scholar
- 11.Weiss L et al. (2016) Microstructure and property of titanium heterogeneous laser welding. Proceedings of the 13th World Conference on Titanium, TMS, p 317–321Google Scholar
- 16.Scheil E (1942) Bemerkungen zur schichtkristallbildung. Z Met 34(3):70–72Google Scholar
- 17.Laheurte P (2003) Contribution à l'étude du comportement pseudo-élastique d'un alliage bêta métastable. Applications aux arcs orthodontiques (in French), Thesis, Université de Metz, FranceGoogle Scholar