Titanium IMI 550-ANN (Annealed)
Heat-treated state
Softer intermediate condition for machining, straightening or further hot working before final ageing.
Values for the ANN condition
Other IMI 550 tempers and conditions
IMI 550 is listed in 5 conditions; see the grade overview at IMI 550.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNThis page Annealed | Softer intermediate condition for machining, straightening or further hot working before final ageing. | 900 | 1,000 | 16 | 32 HRC | — |
Hot rolled | Semi-finished mill stock bought for re-forging or customer heat treatment; properties not guaranteed. | 950 | 1,050 | 12 | 33 HRC | 1.1 % IACS |
forged above beta transus then solution treated and aged | Chosen when higher fracture toughness and crack-growth resistance matter more than smooth fatigue strength and ductility. | 1,010 | 1,110 | 8 | 35 HRC | 1.1 % IACS |
alpha-beta forged then solution treated and aged | Disc, ring and structural forgings; equiaxed alpha-beta structure with balanced strength and fatigue life. | 1,030 | 1,130 | 12 | 35 HRC | 1.1 % IACS |
STADefault Solution treated and aged | Standard supply condition for bar, billet and forgings where maximum strength to 400 °C is needed. | 1,050 | 1,150 | 13 | 36 HRC | — |
What is IMI 550-ANN?
IMI 550-ANN is IMI 550 heat treated to ANN — softer intermediate condition for machining, straightening or further hot working before final ageing. IMI 550-ANN has a yield strength of 900 MPa (131 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 82% of titanium grades. Elongation at break is 16% and the elastic modulus is 115 GPa (16.7 Msi). IMI 550-ANN has a density of 4.6 g/cm³ (0.166 lb/in³), heavier than 87% of titanium grades. It melts at 1,590°C (2,894 °F). STA is the default condition FabDigit quotes; ANN is available on request or by drawing note.
Advantages
- High strength — 900 MPa (131 ksi), better than 82% of titanium grades
Limitations
- Difficult to weld — 25/100, worse than 100% of titanium grades
- Limited formability — 15/100, worse than 93% of titanium grades
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 90% of titanium grades
- Low electrical conductivity — 1.1 % IACS, worse than 78% of titanium grades
IMI 550-ANN properties
Typical room-temperature values for IMI 550-ANN; 10 are specific to this condition. Other listed values are IMI 550 reference data and may not represent this condition. Bars are the position among titanium grades.
Physical3
IMI 550-ANN has a density of 4.6 g/cm³ (0.166 lb/in³), heavier than 87% of titanium grades. It melts at 1,590°C (2,894 °F).
Mechanical16
IMI 550-ANN has a yield strength of 900 MPa (131 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 82% of titanium grades. Elongation at break is 16% and the elastic modulus is 115 GPa (16.7 Msi).
Thermal6
IMI 550-ANN is rated for continuous service to 350°C (662 °F). It conducts heat at 7.1 W/m·K (4.1 BTU/hr·ft·°F), worse than 68% of titanium grades. Thermal expansion is 9.4 µm/m·K (5.22 µin/in·°F).
Electrical3
IMI 550-ANN conducts electricity at 1.1 % IACS, worse than 78% of titanium grades.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), worse than 93% of titanium grades.
Sustainability4
Producing a kilogram of IMI 550-ANN takes about 650 MJ of energy and emits 42 kg of CO₂ — less than 75% of titanium grades. Typical recycled content is 20%.
Manufacturability8
IMI 550-ANN's machinability is poor (20/100, worse than 68% of titanium grades); weldability poor (25/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with IMI 550-ANN
Is IMI 550 easy to machine?
Machine like a high-strength alpha-beta Ti: rigid setups, low surface speed (~20–35 m/min carbide), heavy positive-rake sharp tools, high-pressure flood coolant, never dwell — work-hardening and galling are severe at 350 HV.
Can IMI 550 be welded?
Fusion welding is generally avoided (silicon and aged microstructure embrittle the HAZ); if required use inert-gas-shielded EB/TIG on annealed material followed by full re-solution and ageing.
Can IMI 550 be formed, bent or molded?
Hot work/forge in the 850–950 °C alpha-beta range with controlled cooling; cold forming is impractical, so bend and stretch operations are done hot or by machining from solid.
What surface finishes work on IMI 550?
Grit blast + pickle or chemical mill to remove alpha case after hot work; anodic/conversion coatings for colour and galling control, ion nitriding or hard coatings for wear surfaces.
IMI 550 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Alalpha stabiliser | 3 – 5 | 4 |
| Mobeta stabiliser | 3.5 – 4.5 | 4 |
| Sn | 1.5 – 2.5 | 2 |
| Sicreep/strength enhancement via silicide precipitation | 0.3 – 0.7 | 0.5 |
| Feimpurity limit | ≤ 0.2 | — |
| Oimpurity limit | ≤ 0.2 | — |
| Cimpurity limit | ≤ 0.08 | — |
| Nimpurity limit | ≤ 0.05 | — |
| Himpurity limit | ≤ 0.01 | — |
| Ti | balance | — |
IMI 550-ANN — frequently asked
What is IMI 550-ANN used for?
IMI 550-ANN is typically used for aeroengine compressor blades, discs and high-temperature fasteners. In short: 400 °C service capability; silicon-strengthened alpha-beta Ti; generally not fusion welded.
What is the yield strength of IMI 550-ANN?
IMI 550-ANN has a typical yield strength of 900 MPa (131 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 82% of titanium grades. Strength varies by condition: see the 5 listed tempers.
Is IMI 550-ANN easy to machine?
Not especially — machinability is rated poor (20/100, worse than 68% of titanium grades). Machine like a high-strength alpha-beta Ti: rigid setups, low surface speed (~20–35 m/min carbide), heavy positive-rake sharp tools, high-pressure flood coolant, never dwell — work-hardening and galling are severe at 350 HV.
Can IMI 550-ANN be welded?
Not readily — weldability is rated poor (25/100). Fusion welding is generally avoided (silicon and aged microstructure embrittle the HAZ); if required use inert-gas-shielded EB/TIG on annealed material followed by full re-solution and ageing.
What surface finishes work on IMI 550-ANN?
Grit blast + pickle or chemical mill to remove alpha case after hot work; anodic/conversion coatings for colour and galling control, ion nitriding or hard coatings for wear surfaces.
Can IMI 550-ANN be formed, bent or molded?
Hot work/forge in the 850–950 °C alpha-beta range with controlled cooling; cold forming is impractical, so bend and stretch operations are done hot or by machining from solid.
What is the maximum service temperature of IMI 550-ANN?
IMI 550-ANN is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between IMI 550-STA and IMI 550-ANN?
STA is the default condition — standard supply condition for bar, billet and forgings where maximum strength to 400 °C is needed. ANN: softer intermediate condition for machining, straightening or further hot working before final ageing. Yield strength is 1,050 MPa in STA versus 900 MPa in ANN.
Sources
- IMI 550 (Ti-4Al-4Mo-2Sn-0.5Si) alloy data sheet — IMI Titanium / TIMET UK (1995)
- BS TA 45–48 — Titanium alloy bar, billet and forgings (Ti-4Al-4Mo-2Sn-0.5Si) — BSI (1990)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
- Materials Properties Handbook: Titanium Alloys — ASM International (1994)
- ASM Handbook Vol. 19 — Fatigue and Fracture — ASM International (1996)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.