ATI 13-8 Supertough® Alloy (UNS S13800) is a modification of the standard ATI 13-8 alloy, and has superior fracture toughness and Charpy impact energies, even at cryogenic temperatures. These improvements have been achieved with tighter chemistry controls and thermo-mechanical processing practices. This improved alloy is a martensitic precipitation-hardening stainless steel that has excellent strength, high hardness, and good corrosion resistance. Transverse fracture toughness properties of 120 ksi/in. minimum in the H1000 condition is achieved by tight chemical composition control, low carbon content, and double vacuum melting. The alloy is produced by vacuum induction melting (VIM), followed by vacuum arc remelting (VAR).This melt practice ensures excellent macro and micro-cleanliness, and tight compositional control. The strengthening mechanism (precipitation hardening in a martensitic matrix) makes it possible to achieve uniform strengthening in heavy sections. Strength and ductility levels can be tailored to the application by varying the aging temperature. ATI 13-8 Supertough® Alloy is available as ingot, billet, block, round bar, rolled shapes and rectangles, rolled and drawn rod, and wire. Typical applications are large airframe structural components.