High-strength high-toughness beta type titanium alloy and preparation method thereof

The invention discloses high-strength high-toughness beta type titanium alloy and a preparation method thereof. The beta type titanium alloy is Ti-Al-Fe-V-Cr-Zr system alloy and comprises, by weight, 2.5%-3.5% of Al, 0.85%-1.35% of Fe, 3.5%-5.1% of V, 1.0%-7.5% of Cr, 0.75%- 1.5% of Zr, and less than 0.2% of O. The preparation method of the beta type titanium alloy comprises the following steps that (1) titanium, zirconium, aluminum , Fe-Cr intermediate alloy and Fe-V intermediate alloy are adopted as raw materials, batching is conducted according to weight percentages of all the components, smelting is conducted, and a Ti-Al-Fe-V-Cr-Zr alloy ingot is obtained; (2) the alloy ingot is subjected to cogging at the temperature of 950 DEG C-1050 DEG C, deformation is 60%, repeated cooling is conducted to 750 DEG C-820 DEG C, upsetting and drawing out are conducted, cumulative deformation is 80%, and a bar is obtained; and (3) after the bar is subjected to solution treatment at the temperature of 20 DEG C or 40 DEG C below the alloy phase transformation point for one hour, air cooling is conducted, and then aging is conducted at the temperature of 550-600 DEG C for 6-8 hours. According to the high-strength high-toughness beta type titanium alloy and the preparation method thereof, the Al, Fe, V, Cr and Zr elements are selected and added to the components of the alloy, and the Cr element is used for replacing a small amount of Fe and V elements, so that beta flecks are restrained, and the intermediate alloy serves as the raw materials to reduce the cost of the beta type titanium alloy.