Effects of heat treatment on microstructure and properties of electron beam welded TC4 titanium alloy

For electron beam welding(EBW)of TC4 titanium alloy with different preheat treatments and post-weld heat treatment, microstructure and phase composition characteristics of these welds of TC4 were studied by means of optical microscope and X-ray diffraction.Tension and impact test were carried out at room temperature. The results indicated that the microstructure of two kinds of base metals is the mixture of α phasse and β phase, but their state and distribution are different.The post-weld solution and aged operation carried out in the case of annealed welds leads to a coarsening and homogenous of the acicular α, the microstructures is typically reticular structure.The welds in solid solution state were given a relief annealed after welding, whose microstructure at FZ is tempered martensite α in side prior β grains and at grain boundary α.It induced that the ultimate tensile strength (UTS) of annealed state welds is less than that of solution treated welds, but the impact toughness of the former is greater than that of the latter.However, the UTS and impact toughness of these two kinds of welds are greater that that of base metal.