Solution hardening in niobium

A study has been made of the solution hardening of niobium by tantalum, vanadium, zirconium, and tungsten. It is found that hardening is linear with composition at small concentrations and is simply related to the sum of the atomic size and elastic modulus differences. Agreement with the solution‐hardening model of Fleischer for f.c.c. metals is not exact, however, for the results indicate that the atomic size mismatch, rather than the elastic modulus difference, is the dominant factor in hardening. – Strain‐hardening, strain‐rate sensitivity, and temperature dependence of the flow‐stress are studied, and it is shown that the basic deformation mechanism remains unaltered by solute additions. It is suggested that the solutes raise the long‐range, athermal component of the flow‐stress and reduce the short‐range, thermally‐activated component.