Effect of Electron Beam Welding on the Microstructure and Mechanical Properties of Low-Cost Titanium Alloys

Abstract

An expansion of titanium to mass production industries, such as the automotive, is prevented by its high extraction and production costs (e.g. extraction of titanium from its ores is 15 times and 3 times higher than that of iron and aluminum, respectively). One possible way to reduce the cost of titanium is to use cheaper alloying elements instead of vanadium or niobium to stabilize the body-centered-cubic β-phase. Iron has been considered for the development of few low-cost titanium alloys, such as the Ti–2.8Al–5.1Mo–4.9Fe, Ti-1.5Al-6.3Mo-4.4Fe and Ti-3.6Fe-0.25O alloys, because of its stabilizing effect of the β-phase. Nevertheless, due to the high density of iron, high quantity of β-stabilizing elements and the formation of TiFe-based brittle intermetallic phases, welding joints of low-cost titanium alloys are prone to formation of cold cracks which is very important limiting factor for obtaining welded joints with a strength of at least 90% compared to the strength of base material. Electron Beam Welding with its higher welding speed and intensity used in the process has its advantages over other welding methods in achieving the higher temperature required for melting and joining titanium alloys and obtaining welds with better mechanical properties. In this work the influence of the electron beam welding thermal cycle on the structure and mechanical properties of low-cost titanium alloys Ti–2.8Al–5.1Mo–4.9Fe, Ti-1.5Al-6.3Mo-4.4Fe and Ti-3.6Fe-0.25O will be studied.