Determination of and the effect of heat treatment on the χ parameter of 18R₁ martensite in Cu–Zn–Al alloys

Four experimental methods of determining the x parameter of M18R₁ martensite are described, using X-ray and electron diffraction, including both relative intensity comparison and geometrical measurement. The good agreement of the experimental values of the x parameter determined with these four methods proves their correctness. The x parameters of M18R₁ martensites in Cu–Zn–Al alloys, formed by step quenching and direct quenching, are rather large. They approach the value of 1/3 found in N18R₁ as the aging (after direct quenching) temperature is raised, but they remain unchanged during the aging process after step quenching.