SP-700 (Ti-4.5Al-3V-2Mo-2Fe) Titanium Alloy
Introduction
SP700 (Ti-4.5Al-3V-2Mo-2Fe) is a superplastic titanium alloy developed in Japan, which can be superplasticised and diffusion bonded at 775 ℃. The superplastic forming temperature is lower than that of Ti-6Al-4V alloy, and the tensile and fatigue strengths are better than those of Ti-6Al-4V alloy, so that it can be used to manufacture thin sheet aerospace structural parts. Because it avoids the defects of titanium’s high deformation resistance and poor room temperature plasticity, thus greatly reducing the cost of titanium deformation processing, Japan applies this alloy to the connecting rods of Honda NSX motorbike, and the American RMI Titanium Company manufactures this titanium alloy into structural and rotating parts of aircrafts.
Titanium SP-700 (Ti-4.5Al-3V-2Mo-2Fe) alloy, a new β rich, α + β titanium alloy, has been developed for its superior hot workability and outstanding superplasticity properties, particularly at lower temperatures. The study reports results from mechanical tests at varying temperatures (650, 700, 800 and 900°C of SP-700 (Ti-4.5Al-3V-2Mo-2Fe), at various strain rates (0.01/s, 0.001/s and 0.0001/s) and its corresponding microstructures. It also reports observations of oxidation and formation of alpha-case at around 800 °C.
Chemical Composition (wt.%)
| Elements | Metric Value |
| Aluminum, Al | 4.0 – 5.0 % |
| Carbon, C | <= 0.80 % |
| Hydrogen, H | <= 0.010 % |
| Iron, Fe | 1.7 – 2.3 % |
| Molybdenum, Mo | 1.8 – 2.2 % |
| Niobium, Nb (Columbium, Cb) | 6.5 – 7.5 % |
| Nitrogen, N | <= 0.050 % |
| Other, each | <= 0.10 % |
| Other, total | <= 0.40 % |
| Oxygen, O | <= 0.15 % |
| Titanium, Ti | 87% |
| Vanadium, V | 2.5 – 3.5 % |
| Yttrium, Y | <= 0.0050 % |
Physical Properties
| Physical Properties | Metric Value |
| Density | 4.54 g/cc |
| Mechanical Properties | Metric Value |
| Hardness, Vickers | 315 |
| Tensile Strength | >= 960 MPa |
| Tensile Strength, Yield | >= 900 MPa |
| Elongation at Break | >= 10 % |
| Tensile Modulus | 110 GPa |
| Poissons Ratio | 0.33 |
| Shear Modulus | 41.4 GPa |
| Electrical Properties | Metric Value |
| Electrical Resistivity | 0.000164 ohm-cm |
| Magnetic Permeability | 1.002 |
| Magnetic Susceptibility | 0.00000351 |
SP-700 (Ti-4.5A1-3V-2Mo-2Fe) Advantages
A new β-rich α + β titanium alloy, SP-700, was designed to improve hot workability and mechanical properties over Ti-6A1-4V alloy. The chemical composition of the alloy is Ti-4.5A1-3V-2Mo-2Fe, and particularly enhanced properties include superplasticity, hardenability, and fatigue strength. Owing to its extremely fine microstructure and low β-transus temperature, SP-700 is superplastically formable at temperatures below 1073 K without significant increase in flow stress. More advantageously, diffusion bonding is also accomplished around this temperature. The low temperature SPF/DB process not only saves die material life and process costs, but also reduces alloy degradation from exposure at elevated temperatures, e.g., grain growth and oxidation. Isothermal and conventional hot forging are also performed better with SP-700 than ordinary titanium alloys like Ti6A1-4V.
The alloy is heat treatable and one of its many mechanical properties is that high strength over 1200 MPa is attained in solution treatment and aging condition. The advantage to this is that the moderately stable β phase tolerates air cooling for solution treatment. Thermal distortion in work pieces, which would be caused by rapid cooling, is consequently avoided. In addition, the alloy is cold workable in such cases as rolling and blanking, when annealed around 1073 K. Furthermore, fatigue life and resistance to hydrogen-assisted stress corrosion cracking are improved due to reduced aluminum content.
The superior properties of SP-700 over conventional titanium alloys make new applications possible in non-aerospace fields including sporting goods, hand tools, and wrist watches. Golf drivers, with club heads made of SP-700, are sold commercially. Crampons, a new product of SP-700, withstand cold blanking and bending which reduces production costs and extends life. Due to its high forgeability, SP-700 is expected to extend its application to the production of steam turbine blades. Details of practical applications have been demonstrated together with advantages of properties and fabrication for the blades.
Characteristics
Alpha-beta alloy, beta-rich, fine microstructure, excellent superplastic formability.
Related Standards & Product Form
AMS4964 Ti-4.5Al-3V-2Fe-2Mo Titanium Alloy Bars, Wire, Forgings, and Rings, Annealed
AMS4899 Ti-4.5Al-3V-2Fe-2Mo Titanium Alloy, Sheet, Strip, and Plate, Annealed
Applications
Aerospace components
Metal wood heads
Metal balloons
Tools
Automotive components
Wrist watch casings
Mountain-climbing equipment
Steam Turbine Blades
