Production of Ti–1.5Al–1Mn Titanium Alloy Butt Joints by Friction Stir Welding

A focus towards industrial energy efficiency explains the current interest in light and high-strength materials and welding and processing technologies. Among the latest popular materials are titanium alloys, which are difficult to process and weld. The problem of joining can be solved by friction stir welding. In the present paper, the mechanical properties and structure of a friction stir welded Ti–1.5Al–1Mn titanium alloy were studied. Alloy behavior in friction stir welding is poorly known; therefore, special attention was paid to the welding process—process modes, torque, and axial force. For the first time, Ti–1.5Al–1Mn joints with 92% of their base metal strength were produced by friction stir welding. Additionally, the important role of the axial load in welding was demonstrated. Axial load increases adhesion and mass transfer. A tool made of ZhS32 nickel heat-resistant superalloy received low wear after 1.5 m of welding. A layer with coarse grains was first found in the subsurface of the stir zone—this layer results from repeated recrystallization behind the tool due to the thermal effect of the shoulders and the low thermal conductivity of the material.