Thermally activated solid solution hardening of the ternary system: Nb--Mo- -W. Progress report

The temperature dependence of the flow stress of ultrahigh vacuum degassed Nb-Mo-W single crystals has been investigated between 77 and 900 K. Tests of alloys containing up to 9.4 a /o (Mo+W) show that the thermal component of the flow stress exhibits little or no increase with increasing ternary solute content for most of the alloys tested.Solid solution softening is observed in the Nb-4.2Mo-W alloys at 77 K.The results"are interpreted utilizing a phenomenological analysis of the solid solution hardening of ternary alloys in terms of binary alloy hardening increments.The analysis of the results suggests that a non-random solute distribution is responsible for reducing the thermal activated flow stress component, especially in concentrated alloys in which the Mo to W ratio is near unity.