The effect of deformation on the magnetoelastic properties of iron-nickel alloys, and some implications concerning current theories of invar behaviour

Elastic modulus, saturation magnetisation, and Curie temperature measurements have been made on Nispan C and binary 42% Ni alleys after varying degrees of deformation between 0 and 55%. Deformation preduces an increase in modulus (7%) and a substantial reductien in saturatien magnetisation (12%), but only a relatively small change in Tc(2%). The ΔE effect is reduced by deformation, in marked contrast to the effect preduced by ageing. Since Nispan C behaves almost identically to the binary alley, these changes cannot be attributed to deformation-induced precipitation of intermetallic compounds. A modified two gamma states medel is found to explain the observations in a reasonably quantitative manner.