Ribbons of nominal composition Co80Nb8B12 have been prepared by the single roller quenching method using different wheel velocities ranging from 26 to 42 ms−1. X-ray diffraction patterns for ribbons prepared at low velocities show crystalline peaks but characteristic for the amorphous state for samples prepared at velocities above 36 ms−1. Room-temperature values of the magnetostriction constant lambdas depend on the quenching rate and changes from 4×10−7 to −1×10−6 as the wheel speed increases. Zero magnetostriction samples are obtained at about 34 ms−1. Thermal treatments change the values of the magnetostriction in the same way as a decrease in the quenching rate does. A dependence of the magnetostriction constant on the applied stress has been found. This dependence, fully reversible, is observed at room temperature. Journal of Applied Physics is copyrighted by The American Institute of Physics.