A study of thermal stability in electrodeposited nanocrystalline Fe-Ni invar alloy

Highlights: → Thermal stability and grain growth kinetics of a NC Fe-Ni invar alloy were studied. → The alloy showed good stability to 0.36Tm and abrupt grain growth happened above that. → The activation energies indicated different growth mechanisms below and above 0.36Tm. → Below 0.36Tm, grain boundary re-ordering may act as the grain growth mechanism. → Above 0.36Tm, grain boundary diffusion may act as the grain growth mechanism. - Abstract: The grain growth of an electrodeposited nanocrystalline Fe-Ni invar alloy was studied with differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results showed very limited grain growth below the temperature of 0.36Tm, and the activation energy was 40 ± 3 kJ/mol in the low temperature range, which implied the possible mechanism of grain growth as re-ordering of grain boundaries; an abrupt grain growth happened above 0.36Tm with a DSC exothermic peak detected, of which the heat release was about 14 ± 2 J/g; at temperatures above 0.36Tm, the grain growth activation energy was obtained through Kissinger analysis and isothermal kinetics analysis, both of the results suggested the grain growth mechanism as grain boundary diffusion.