Abstract
Young's modulus and its change by magnetization in annealed γ-phase Ni-Co alloys were measured with the method of magnetostrictive vibration. The ΔE-effect in alloys of low cobalt content (0_??_15% Co) is positive up to its saturation, while the effect in alloys of high cobalt content (21_??_59% Co) is negative at low fields, and then becomes positive at higher fields. These i egative ΔE-effects are far more conspicuous than those hitherto known. The saturation valces of the ΔE-effect, positive for all alloys, show two maxima and two minima. The first maximum at 3% Co amounts to about 28%, this being the highest value of the ΔE-effect found at ordinary tenperatues. Yeung's moduli at demagnetized and saturated states changes similarly with composition and both show sharp minima at 3_??_4% Co.
