The Paton Welding Journal, 2013, #3, 24-27 pages
MATHEMATICAL MODELLING OF STRUCTURAL TRANSFORMATIONS IN HAZ OF TITANIUM ALLOY VT23 DURING TIG WELDING
S.V. AKHONIN, V.Yu. BELOUS, A.F. MUZHICHENKO and R.V. SELIN
E.O. Paton Electric Welding Institute, NASU, Kiev, Ukraine
Issues of weldability of multi-component titanium alloys are covered
in many studies. As experimental investigations are time- and labour-consuming,
it seems reasonable to use mathematical methods for evaluation of the effect
of parameters of the welding thermal cycle on structural transformations
occurring in the HAZ. In the present study the effect of the thermal cycle
of argon-arc welding on shape and size of the weld, length of HAZ and
kinetics of structural transformations in the HAZ metal is investigated
by the mathematical modelling methods by an example of TIG welding of
high-strength titanium alloy VT23. Calculations using the 3D mathematical
model of the thermal processes occurring in titanium during welding,
based on the differential thermal conductivity equation, were carried out
by employing the finite element method application package.
The calculations made it possible to determine size and shape
of the weld and HAZ, in which the polymorphic transformations
take place to form the &alfa;''-, &alfa;''- and β''-phases. The calculations
showed that the a&alfa;''-phase may form in the weld metal at the highest
cooling rates. The low-ductility ω''-phase does not form at the
investigated process parameters and welding speeds of 10 m/h because
of comparatively low cooling rates within the 500-600 °C temperature range.
The results obtained can be applied in development of the technology for
welding of advanced titanium alloys. 4 Ref., 6 Figures.
TIG welding, mathematical modelling, titanium alloy, cooling rate, polymorphic transformations
1. Gurevich, S.M., Zamkov, V.N., Blashchuk, V.E. et al. (1986) Metallurgy and technology of welding of titanium and its alloys. Kiev: Naukova Dumka.
2. Akhonin, S.V., Belous, V.Yu., Muzhychenko, A.F. (2009) Narrow-gap TIG welding of titanium alloys with electromagnetic redistribution of thermal energy of the arc. In: Proc. of 4th Int. Conf. on Laser Technologies in Welding and Materials Processing (26-29 May, 2009, Katsiveli, Crimea, Ukraine), 11-13.
3. Lyasotskaya, V.S., Lyasotsky, I.V., Meshcheryakov, V.N. et al. (1986) Phase transformations in continuous cooling in VT6ch and VT23 alloys. Tsvet. Metallurgiya, 2, 88-93.
4. Lyasotskaya, V.S. (2003) Heat treatment of titanium alloy welded joints. Moscow: Ekomet.