Abstract: An alloy suitable for making single crystal castings consists essentially of the following constituents by weight percent:______________________________________ Chromium 8-15% Aluminum 5-7% Titanium 2-5% Niobium 0.1-2% Molybdenum 0-7% Tantalum 1-8% Tungsten 0-7% Cobalt 5-15% Vanadium 0.5-2% Carbon 0-0.05% Balance Nickel plus impurities. ______________________________________The combined weight of Tungsten, Molybdenum and Tantalum is from 2.5 to 8.0 percent by weight of the total alloy weight and the combinations of Aluminium, Titanium, Niobium, Tantalum and Vanadium are balanced such as to give an alloy volume fraction of between 60 and 75% of gamma prime (Ni.sub.3 (M)) where M is Aluminium, Titanium, Niobium, Tantalum, Vanadium and also minimum gamma/gamma prime lattice mismatch. The alloy has good high strength characteristics, impact resistance, corrosion and oxidation resistance and has a wide heat treatment window.

Abstract: A relatively low-density Nickel based superalloy particularly suitable for use in the form of a single crystal casting comprised by weight percent:Chromium: 7-13%Aluminium: 5-7%Titanium: 2-5%Cobalt: 4-16%Molybdenum and/or Ruthenium: 1-4%Vanadium: 0-2%Carbon: 0-0.05%Balance Nickel plus incidental impurities, the density of the alloy being less than 7.9 kg/dm.sup.3.