Comparison of Titanium Alloy ---Ti-6Al-4V(Grade 5) and Ti-3Al -2.5V(Grade 9) / UNS R56400 and UNS R56320
Grade 9 Ti 3Al 2.5V alloy is an alpha-beta alloy that has improved strength over commercially pure titanium grades. This grade also has excellent corrosion resistance, formability and weldability.
Grade 5 Ti-6Al-4V alloy is the most widely used of all the titanium grades. It is a medium to high strength general-purpose alloy. It is also referred to as an alpha-beta alloy. This alloy is fully heat treatable in sections measuring up to 15mm. It can be heated up to 400°C (750°F), and has good tensile properties at room temperature, creep resistance up to 325°C and very good fatigue strength. It is also known to be highly resistant to general corrosion in sea water.
Grade 5 Ti-6Al-4V 2mm Sheet According to AMS 4911
Grade 9 Ti 3Al 2.5V Seamless tube according ASTM B338
Machinability
GR5-Although tough, grade 5 Ti-6Al-4V alloy can be machined using the right quantity of coolant flow, slow speeds and high feed rates. High speed tools should be used for tooling this alloy and the recommended tool types are tungsten carbide designations C1-C4 or cobalt based.
GR9-Although tough, grade 9 Ti 3Al 2.5V alloy can be machined using the right quantity of coolant flow, slow speeds and high feed rates. High-speed tools should be used for tooling this alloy and the recommended tool types are tungsten carbide designations C1-C4 or cobalt based.
Forming
Gr5-Grade 5 Ti-6Al-4V alloy can be hot or cold formed. The forming techniques include hydropress, stretch or drop-hammer.
GR9-Grade 9 Ti 3Al 2.5V alloy can be hot or cold formed using hydropress, power brake, stretch or drop hammer techniques.
Welding
Gr5-Weldability of grade 5 Ti-6Al-4V alloy is rated as fair.
GR9-Weldabilty of grade 9 Ti 3Al 2.5V alloy is rated as good.
Annealing
Gr5-Annealing can be performed by holding at 732°C (1350°F) between 1/4 and 4 h, then furnace cooled to 566°C (1050°F) followed by air cooling. In case of forgings and bars, furnace cooling is not required.
GR9-The material can be fully annealed at 593-760°C (1100-1400°F) for 3 h, and then air cooled. For stress relief, the material has to be heated to 316-649°C (600-1200°F) for 3 h and air cooled.
Heat Treatment
Gr5-Solution treatment of the material is done at 904-954°C (1660-1750° F) for 2 h, which is followed by water quench process.
GR9-The material has to be solution heat treated to 871-927°C (1600-1700°F), then held for 15-20 min and water quenched.
Forging
Gr5-Rough forging of grade 5 Ti-6Al-4V alloy should be performed at 982°C(1800°F), and finished at 968°C (1750°F).
Gr9-Rough forging can be performed at 900°C (1650°F) and completed at 843°C (1550°F).
Hot Working
Gr5-Hot working enhances the overall ductility of the material.
Gr9-Hot working enhances the overall ductility of the material.
Cold Working
Gr5-Cold working features of this material is same as that of a moderately tempered austenitic stainless steel. Post-work annealing is recommended to re- attain favorable performance properties.
Gr9-Cold working features of this material is same as that of austenitic stainless steel. Post-work annealing is recommended to re-attain favorable performance properties.
Aging
Gr5-Aging of grade 5 Ti-6Al-4V alloy can be performed at 538°C (1000°F) for 4 h, and then air cooled.
Gr9-For aging grade 9 Ti 3Al 2.5V alloy, the material should be heated to 482-510°C (900-950 °F) for 2 to 8 h and then air cooled.
Applications
Gr5-Grade 5 Ti-6Al-4V alloy is a popular titanium alloy and is widely used in several industries including aerospace, power generation, marine, and offshore industries.
Gr9-Grade 9 Ti 3Al 2.5V alloy is used in the following application areas:
-For tubing in aircraft and engine hydraulic systems
-Golf clubs and tennis rackets
-Performance bicycles
Cold working features of this material is same as that of a moderately tempered austenitic stainless steel. Post-work annealing is recommended to re- attain favorable performance properties.
Comparison Tables of Mechanical Properties and Chemical Composition
| Mechanical Properties | |||
| Grade | Tensile stength MPA(min) | Yield strength MPA (min) | Elongation % (min) |
| Gr5/UNS R56200 | 895 | 828 | 10 |
| Gr9/UNS R56320 | 620 | 483 | 15 |
| Chemical Composition | ||||||||
| Grade | Elements comtent %(max) | |||||||
| Fe | O | N | C | H | Al | Va | Ti | |
| Gr5/UNS R56200 | 0.4 | 0.2 | 0.05 | 0.08 | 0.015 | 5.5-6.75 | 3.5-4.5 | Balance |
| Gr9/UNS R56320 | 0.25 | 0.15 | 0.03 | 0.08 | 0.015 | 2.5-3.5 | 2.0-3.0 | |
Equivalent materials to grade 5 Ti-6Al-4V alloy and grade 9 Ti 3Al 2.5V alloy are as follows:
| Gr5 | AMS 4928 | AMS 4965 | AMS 4967 | MIL T-81915 | MIL T-9046 |
| AMS 4920 | AMS 4954 | ASTM B265 | MIL T-81556 | MIL T-9047 | |
| AMS 4911 | AMS 4935 | ASTM B348 | MIL F-83142 | SPS M618 | |
| AMS 4906 | AMS 4934 | ASTM B381 | GE C50TF12 | DMS 1570 | |
| AMS 4905 | AMS 4930 | DIN 3.7164 | |||
| Gr9 | AMS 4943 | AMS 4944 | AMS 4954 | ASTM B337 | |
| ASTM B338 | ASTM B348 | ASTM B381 | ASTM B265 | ||
| GE B50TF117 | MIL T-9046 | MIL T-9047 | PWA 1260 | DMS 2241 |
Thermal Properties of grade 5 Ti-6Al-4V alloy and grade 9 Ti 3Al 2.5V alloy are tabulated below.
| Properties | Metric | Imperial | |
| grade 5 Ti 6Al 4V | Thermal expansion co-efficient (@0.000-100°C/32-212°F) | 9 µm/m°C | 5 µin/in°F |
| Thermal conductivity | 6.60W/mK | 45.8 BTU in/hr.ft².°F | |
| grade 9 Ti 3Al 2.5V | Thermal expansion co-efficient (@20-95°C/68-203°F) | 9.61 µm/m°C | 5.34 µin/in°F |
| Thermal conductivity | 8.30 W/mK | 57.6 BTU in/hr.ft².°F |