The Deformation of Niobium Alloys Containing Mo and Ta in Solid Solution

Abstract

Ultra-high vacuum annealed Nb-Ta and Nb-Mo crystals were tested in compression at temperatures between 4.2 K and 373 K. Small amounts of either alloying element completely suppressed the anomalous slip which takes place in pure niobium below about 150 K. At room temperature and above Ta had little effect on the yield and flow stresses whereas Mo gave considerable hardening and extended the thermal stress region. At low temperatures, both elements increased the yield stress values but the flow stress curves tended to merge as the temperature decreased. Ta had very little effect on the force-distance curves but Mo additions extended the width, especially at low stresses. Overall the effects of Ta may be rationalised through its effect on anomalous slip whereas Mo has additional solute-dislocation interactions due to its size difference.