This specification covers an iron-nickel alloy in the form of strip. This strip has been used typically for diaphragms, leaf springs, and helical springs, requiring a precipitation-hardenable alloy with a coefficient of modulus of elasticity of -20 to +20 x 10\u-<(hoch)6> per degree Fahrenheit from -50 to +150F (-36 to +36 x 10\u-<(hoch)6> per degree Celsius from -46 to +66C) after suitable heat treatment.