Ti-17 titanium alloy bar forging process research

Titanium alloys are widely used in aerospace applications due to their high specific strength, corrosion resistance and excellent thermal strength, etc. The Ti-17 alloy is a near-beta 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 high strength, hardenability and fracture toughness, but also has good thermal stability, fatigue properties, hot working properties. Since the 1970s, it has been able to enter the aerospace industry with excellent performance and used as a compressor for higher thrust engines. With the continuous development of China's engine industry, with Ti-17 titanium forgings produced by the high-pressure compressor first and second overall disc forgings Ti-17 titanium bar specifications, organization and performance have higher requirements. For this reason, researchers have studied the forging process of Ti-17 titanium alloy Φ350mm large bar.

The phase transition point (α+β/β) of the experimental material alloy was determined to be 880~900℃ by metallographic method.

The Φ350mm specification bar was produced according to two forging process schemes A and B. Scheme A: Ingot single-phase deformation for upsetting, deformation of 60-75%, then enter the two-phase zone forging, two-phase zone for normal drawing process, deformation of 60-75% ; Scheme B: Ingot forging by normal drawing process, single-phase deformation of 40-65%, two-phase deformation of 40-60%. The study shows:

(1) The mechanical properties of Ti-17 Φ350mm bar forged by scheme A are all in accordance with the standard requirements. The high-temperature tensile properties and creep properties of the forged bar produced by scheme B do not fully meet the index requirements.

(2) The forged bar produced by scheme A, low times for uniform fuzzy crystal, high times for spherical α + β transfer organization, transverse longitudinal microstructure is not significant. Scheme B production of forged bar low times for homogeneous semi-fuzzy crystals, high-order organization for spherical α + lamellar α + massive α + β transfer organization, the longitudinal organization has a tendency to be different, transverse vertical microstructure for the different.

(3)The detected clutter level of forged rods produced by scheme A can be up to Φ3.2 -9 to -12 dB, and the detected clutter level of forged rods produced by scheme B is Φ3.2 0 to -3 dB.The overall clutter level is higher, -6 to -9 dB.

(4) Through the upsetting process, single-phase deformation of more than 60%, two-phase zone with long deformation, and the deformation of more than 60% of the forging process, you can produce products with performance, organization and inspection level in line with the standard requirements. The user requires Ti-17 titanium alloy Φ350mm specification bar, which is suitable for industrialized mass production.