Heat treatments, microstructure and properties of internal-tin Nb3Sn

摘要

The decrease of temperature ramp rate during heat treatments of the internal tin process causes an increase of the critical current density at low and medium magnetic fields (4-16T). This paper investigates the metallurgical origin of this benefit by considering the effects of a change of heating rate on the phase transformations of bronze and on the filament recrystallization. The low temperature formation of Nb3Sn is important for the critical current density of this material. This is explained by the composite microstructure evolution