Form This specification covers an iron-nickel alloy in the form of strip 0.020 to 0.250 inch (0.51 to 6.35 mm) inclusive@ in thickness (see 8.8). Application This strip has been used typically for diaphragms@ leaf springs@ and helical springs@ requiring a precipitation-hardenable alloy with a thermoelastic coefficient of -20 to +20 x 10-6 per degree Fahrenheit from -50 to +150 ??(-36 to +36 x 10-6 per degree Celsius from -46 to +66 ?? after suitable heat treatment@ but usage is not limited to such applications.