Preparation method capable of synchronously improving strength and plasticity of additive manufactured titanium alloy

The invention discloses a preparation method capable of synchronously improving strength and plasticity of an additive manufactured titanium alloy. The preparation method comprises the following steps: (1) Ti-6Al-4V alloy powder with a particle size of -90-+325 meshes is put in a powder feeder, wherein the oxygen content of the powder is not higher than 0.20 wt.%; (2) a substrate is fixed on a worktable of an argon-charged inert atmosphere machining chamber; (3) in the argon-charged inert atmosphere machining chamber, when the oxygen content is lower than 100 ppm, a titanium alloy is formed through additive manufacturing; and (4) under the effect of a laser source, the synchronously fed Ti-6Al-4V alloy powder is continuously molten and deposited on the substrate; in the deposition process, the energy density of the deposition area and the size of the deposition area are controlled to obtain 103-104 k/s cooling speed in the liquid-solid transformation process and to obtain 100-400 k/s cooling speed in the process of converting from a beta phase to an alpha phase; and a Ti-6Al-4V alloy part with an alpha/beta interface phase is prepared.