INCOLOY® alloy 903 (UNS N19903) is an agehardenable nickel-iron-cobalt alloy whose outstanding characteristics are a constant low coefficient of thermal expansion, a constant modulus of elasticity, and high strength. The nominal composition is shown in Table 1. The alloy’s characteristics make it an excellent candidate for applications such as rocket-engine thrust chambers, steam-turbine bolts, springs, gage blocks, and ordnance hardware. Table 1 - Limiting Composition, wt % Nickel ..........................................................................36.0-40.0 Cobalt..........................................................................13.0-17.0 Aluminum ....................................................................0.30-1.15 Titanium.......................................................................1.00-1.85 Niobium.......................................................................2.40-3.50 Iron ...............................................................................Balance* Table 2 - Physical Constants of Age-Hardened  INCOLOY alloy 903 Density, lb/in3 .....................................................................0.298 g/cm3 ......................................................................8.25 Curie Temperature °F.....................................................................780-880 °C ....................................................................416-471 Melting Range °F.................................................................2405-2539 °C ................................................................1318-1393 *Reference to the ‘balance’ of an alloy’s composition does not guarantee this is exclusively of the element mentioned, but that it predominates and others are present only in minimal quantities.