Microstructural evolution in Ti-6Al-4V alloy joints using the process of friction stir spot welding

ABSTRACT

Friction Stir Spot Welding (FSSW) is a subject that has recently gained interest and been developed, mainly in Titanium alloys, since there are existing studies on alloys of aluminium, magnesium, steels and polymers. Titanium alloys are widely used in the aeronautical industry, mainly as components of undercarriages for commercial planes. This work focuses on the Ti-6Al-4V alloy; this type of alloy has alpha (α) and beta (β) phases and provided better balance in terms of the mechanical properties of hardness and tensile stress. The FSSW process was performed using a high-speed machining centre, using a rotational speed of 500 RPM, a plunge speed of the tool of 2 mm/s and 3 s as dwell time, on plates with a thickness of 1.5 mm and an overlap length of 20 mm. The results showed the effect of the variables of the FSSW welding process on the microstructure of the Ti–6Al–4V alloy caused by the thermal effect and the plastic deformation of the welding process, concluding that the right combination of parameters provides a joint without any defects.

KEYWORDS:

• Ti-6Al-4V alloy
• microstructural analysis
• Friction Stir Spot Welding (FSSW)
• aeronautical alloys
• thermo-mechanically affected zone

Acknowledgments

The authors would like to thank the Centro de Investigación e Innovación en Ingeniería Aeronáutica de la Facultad de Ingeniería Mecánica y Eléctrica de la Universidad Autónoma de Nuevo León and the Corporación Mexicana de Investigación en Materiales S.A de C.V, for providing the facilities used to develop this research. Flor Araceli García-Castillo would like to thank PROMEP for the postgraduate scholarship.