| Ti6Al4V titanium alloy has been widely used in the fields of aircraft and chemical industy because of its high strength-to-weight ratio, superior corrosion resistance, creep resistance at high temperature, no magnetism and so on. Compared with the tradition welding method, the electron beam welding has some characteristics such as high energy density, small welding deformation and high efficiency, which has becomed one of advanced welding technique and important research directions.The microstructures of TC4 titanium alloy electron beam welding (EBW) joints was studied in this paper; The simulation test was made by means of the welding thermal simulation technique to research the influences for the final state in tissue transformation and the law of the grain growth in different cooling rates.The research of TC4 titanium alloy electron beam welding has found that the grains in the fusion zone are mainly equiaxedβcolumnar grains, the sizes of these equiaxed grains decrease successively from the top to the bottom of the joints. The main microstructures in the equiaxed grains areα′martensite;The result of thermal simulation shows the lamellarαis growth along theβgrain boundary under the low cooling rate. As the cooling rate is increased, the acicularα′martensite is formed with theα-phase reduction; XRD analysis indicates the diffraction peaks of the hexagonal close packed (hcp) crystalαandα′phase offset a small angle between the base metal and the sample; The microhardness is higher with the increase of cooling rate, but strengthening effect is not obvious.The result of TC4 titanium alloy with different heat treatment shows thatα-phase is not completely transformed intoβ-phase, equiaxed primaryα-phase is found under 970℃which is slightly below theβtransition temperature; As the heating temperature is higher than the phase transition temperature, the lamellarαis smaller with the increase of cooling rate, acicular martensite is found under water quenched.
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