Titanium alloy due to high specific strength, corrosion resistance and excellent thermal strength, etc., in the field of aerospace has been widely used. Ti-17 alloy is a kind of near-β-type alloy with excellent properties. Its nominal composition is Ti-5Al-2Sn-2Zr-4Mo-4Cr. The alloy can be forged in the α + β phase region or in the β phase region. It not only has a high strength, hardenability and fracture toughness, and good heat stability, fatigue performance, thermal processing performance. Since the 1970s, it has been able to enter the aerospace industry with excellent performance and used it as a compressor for higher thrust engines. With the continuous development of China's engine industry, with Ti-17 titanium forging production of high-pressure compressor first and second overall disc forging Ti-17 titanium rod bar specifications, organization and performance have a higher Claim. To this end, the researchers studied the Ti-17 titanium alloy Φ350mm large-scale bar forging process.
The phase change point (α + β / β) of the experimental material alloy was 880 ~ 900 ℃ by metallographic method.
According to A, B two forging process program production Φ350mm specifications bar. Option A: The ingot is deformed in a single phase for upsetting, the deformation is 60-75%, then enters the two-phase area forging, the two-phase area performs the normal drawing process, the deformation amount is 60-75%; the plan B: The ingot is forged by normal drawing process, the deformation amount of single phase is 40 ~ 65%, and the deformation amount of two phase is 40 ~ 60%. Research indicates:
(1) the use of program A forging Ti-17Φ350mm bar, the mechanical properties are in line with standard requirements. The high-temperature tensile properties and creep properties of the forged bars produced by Scheme B did not fully meet the requirements of the index.
(2) the use of program A production of forging bar, low times for the uniform fuzzy crystal, high-order tissue are spherical α + β transfer tissue, transverse vertical microstructure is not significant. The low magnification of the forging bar produced by scheme B is homogeneous semi-fuzzy crystal, the high-order tissue is spherical α + flake α + block α + β transfer organization, the longitudinal organization has certain tendency, and the transverse vertical microstructure is different.
(3) The level of clutter detection for the forging bar produced by scheme A can reach Φ3.2 -9 ~ -12dB, and the level of forging stick detection clutter produced by scheme B is Φ3.2 0 ~ -3dB. The overall clutter level is high, -6 ~ -9dB.
(4) through the upsetting process, single-phase deformation of more than 60%, two-phase area with long deformation, and deformation of more than 60% of the forging process, can produce performance, organization and testing levels meet the standards and user requirements Ti-17 titanium alloy Φ350mm specifications bar, suitable for industrial mass production.