Whatever happened to Nb3Zr?

A systematic study of the effects of cold work and precipitation on the critical current density of an Nb-27at.%Zr alloy is reported. Heavy cold working, leading to a reduction of more than 99% in the area by swaging and wire drawing increases Jc in a transverse magnetic field of 4 T by a factor of about 13 relative to Jc for the recrystallized alloy. Precipitation of β-Zr, in combination with cold work, further enhances Jc. The highest level of Jc results when the precipitation heat treatment is given at an intermediate stage of working. Such a process in this study gives a value of Jc at H = 4 T, that is more than five times higher than Jc in the most heavily cold-worked specimen. Optical metallographic examination reveals that deformation twinning takes place in this alloy and that precipitation of β-Zr occurs preferentially at deformation twin boundaries.