Effect of dissolved tungsten on the deformation of 70Ni-30Fe alloys

A series of Ni-Fe alloys containing various levels of tungsten in solid solution have been prepared as a means to assess the influence of solid solution strengthening on the mechanical behavior of monolithic 70Ni-30Fe. In particular, 70Ni-30Fe alloys plus equilibrium concentrations of tungsten in solid solution nominally correspond to the compositions associated with the matrix-only portion of certain tungsten heavy alloys, that is, alloys comprised of a high volume fraction of nominally pure tungsten particles embedded within a minority Ni-Fe-W based matrix. The study shows that the working solubility of tungsten within the 70Ni-30Fe base composition increases slightly with temperature, from approximately 21 wt pct at room temperature to approximately 23 wt pct at 1400 °C. Increasing the level of tungsten in solid solution leads to increases in room-temperature yield strength, tensile strength, and ductility. In contrast, the deformation characteristics of the alloys, as quantified by the power-law work-hardening exponent, n, and the strain-rate-sensitivity exponent, m, show little variation with tungsten solute concentration.