Abstract
Ti6Al4V titanium alloy is applied extensively in the aviation, aerospace, jet engine, and marine industries owing to its strength-to-weight ratio, excellent high-temperature properties and corrosion resistance. In order to extend the application range, investigations on welding characteristics of Ti6Al4V alloy using more welding methods are required. In the present study, Ti6Al4V alloy sheets were joined using resistance spot welding, and the weld nugget formation, mechanical properties (including tensile strength and hardness), and microstructure features of the resistance spot-welded joints were analyzed and evaluated. The visible indentations on the weld nugget surfaces caused by the electrode force and the surface expulsion were severe due to the high welding current. The weld nugget width at the sheets’ faying surface was mainly affected by the welding current and welding time, and the welded joint height at weld nugget center was chiefly associated with electrode force. The maximum tensile load of welded joint was up to 14.3 kN in the pullout failure mode. The hardness of the weld nugget was the highest because of the coarse acicular α′ structure, and the hardness of the heat-affected zone increased in comparison to the base metal due to the transformation of the β phase to some fine acicular α′ phase.
Highlights
Ti6Al4V titanium alloy is widely used in the aerospace, marine, pressure vessel, and chemical industries, as well as for surgical implant, etc., owing to its unique properties, such as a high strength-to-weight ratio, excellent high-temperature properties and corrosion resistance; the usage of Ti6Al4V alloy accounts for over 50% of the total titanium alloy tonnage, globally [1,2,3,4,5]
The plasma arc welding process is a high-energy beam welding technology, and is utilized to weld the butt joint of thicker titanium alloy plate, which is similar to the laser welding process [10]
Visible indentations could be seen on the weld nugget surfaces for all welded joints, which surface owing tohigh the temperature high temperature and applied thethe sheets’
Summary
Ti6Al4V titanium alloy is widely used in the aerospace, marine, pressure vessel, and chemical industries, as well as for surgical implant, etc., owing to its unique properties, such as a high strength-to-weight ratio, excellent high-temperature properties and corrosion resistance; the usage of Ti6Al4V alloy accounts for over 50% of the total titanium alloy tonnage, globally [1,2,3,4,5].Many welding methods, such as tungsten inert gas welding (TIG) [6,7], laser welding [8], electron beam welding [9], plasma arc welding [10], line friction welding [11,12,13], and friction stir welding [14,15]have been employed to weld titanium alloy in previous investigations.Based on the existing literature, the TIG welding process is always used to weld butt joints of Ti6Al4V titanium alloy, but the weld structure is coarse, inducing high welding residual stress and distortion. Ti6Al4V titanium alloy is widely used in the aerospace, marine, pressure vessel, and chemical industries, as well as for surgical implant, etc., owing to its unique properties, such as a high strength-to-weight ratio, excellent high-temperature properties and corrosion resistance; the usage of Ti6Al4V alloy accounts for over 50% of the total titanium alloy tonnage, globally [1,2,3,4,5] Many welding methods, such as tungsten inert gas welding (TIG) [6,7], laser welding [8], electron beam welding [9], plasma arc welding [10], line friction welding [11,12,13], and friction stir welding [14,15]. Line friction welding has been used to join titanium alloy bulk plates or parts because of its own process principles and Metals 2017, 7, 424; doi:10.3390/met7100424 www.mdpi.com/journal/metals
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