Complete Process Analysis Of Grade 9 Titanium Alloy

Grade 9 titanium alloy is a medium-strength α-β titanium alloy according to its excellent cold formability, weldability, and corrosion resistance. It is a critical material for aerospace tubes, high-end medical devices, and automotive lightweighting. Its production involves complex processes such as vacuum metallurgy, hot and cold plastic deformation, precision heat treatment, and surface treatment. Process parameters directly affect microstructural uniformity, mechanical properties, and service life.

 

 

Grade 9 titanium alloy  has a composition of Ti-3Al-2.5V, with strict low-level control of impurities such as C, N, H, O, and Fe.

Raw material: High-purity sponge titanium is used as the main raw material, with Al-V master alloy added to introduce alloying elements and prevent compositional segregation. Auxiliary materials are treated to remove scale and oil contamination for cleanliness.

 

Proportioning: Raw materials are accurately weighed to the standard composition range, then mixed in a vacuum mixer under argon protection for 4–6 hours to ensure uniformity and eliminate elemental enrichment.

 

Electrode compaction: The mixed powder is cold-pressed into electrode blocks, then welded and assembled into consumable electrodes. Surfaces must be smooth and crack-free to avoid melting defects.

 

 

Titanium is chemically reactive and prone to embrittlement via reaction with oxygen, nitrogen, and hydrogen at high temperatures.

Conducted in an arc furnace with a vacuum level ≤5×10⁻³ Pa. The electrode is melted by arc heat, and the molten metal solidifies in a water-cooled copper crucible to form an initial ingot, removing volatile impurities while retaining slight segregation.

 

The initial ingot serves as the electrode for repeated vacuum melting. Multiple melting-solidification cycles eliminate segregation, refine grains, and control interstitial impurities to ppm levels, yielding a dense, homogeneous Grade 9 titanium ingot.

 

 

Titanium ingots are processed by high-temperature forging and rolling to break up coarse as-cast structures, refine grains, and produce basic profiles including bars, tubes, and sheets.

 

The ingot is heated, held, and fast-forged in multiple passes with a total deformatin into a bar billet, improving toughness and ductility via grain refinement.

Tubes: Bar billets are pierced and hot-rolled into mother tubes, then cold-rolled in multiple passes to control wall thickness and enhance strength.

Sheets: Forged billets are hot-rolled to target thickness, then cold-rolled to optimize dimensional accuracy and surface finish.

 

 

Heat treatment is critical for balancing strength, ductility, and toughness in Grade 9 titanium alloy.

Full annealing

Heating to 700–790 °C, holding for 1–2 hours, furnace cooling to 500 °C, then air cooling. Relieves internal stress, enables recrystallization, and produces an equiaxed α+β microstructure with excellent cold formability. Tensile strength: 620–790 MPa, elongation ≥15%.

 

Solution treatment + aging

Heating to 850–900 °C, holding for 1 hour, water or air cooling to obtain a supersaturated β matrix.

Heating to 500–550 °C, holding for 4 hours, then air cooling to precipitate nano-scale fine α phase, significantly increasing strength to 950–980 MPa with elongation ≥10%. Graded aging achieves a better balance of high strength and toughness.

 

 

Immersion in a mixed HF-H₂SO₄-HNO₃ acid solution for 1–3 hours to remove scale and surface contamination, followed by cleaning and drying.

Boring of tube inner bores, turning, and grinding of bars and sheets to eliminate surface defects and ensure dimensional accuracy.

Coating with anti-rust oil or vacuum packaging to prevent oxidation and contamination during storage and transportation.

 

 

CNC turning, milling, grinding, and drilling with precision up to ±0.01 mm, suitable for aerospace fasteners, medical implants, and other precision components.

 

TIG welding and electron beam welding are commonly used with full argon protection. Post-weld stress-relief annealing at 700–750 °C for 1 hour achieves weld strength ≥90% of the base metal.

 

Grade 9 titanium alloy powder in 3D printing formed into complex structural parts via SLM. Stress-relief annealing at 800 °C after forming, ideal for personalized medical and aerospace special-shaped components.

 

 

Strict inspections are performed at each stage to meet ASTM B338 and AMS 4957 standards:

• Spectrometer testing of main elements and impurity content.
• Metallographic examination of grain and α+β phase uniformity.
• Tensile, impact, and fatigue tests to verify strength and toughness.
• Ultrasonic and eddy current inspection for internal cracks and inclusions.

 

 

 

Ruihang, as a direct factory of titanium products production, is specilized in R&D,production. The company is located in " China's Titanium Valley" , boosting the titanium industry in the world. If you have purchasing needs on hand, feel free to contact us: Sam.Rui@bjrh-titanium.com.