Abstract
The grain growth of the sputtered Ni-30Cr-5Al and Ni-30Cr-5Al-1Y (wt%) nanocrystalline alloys during temperature rising to and isothermally holding at 1000 °C in Ar has been investigated by transmission electron microscope (TEM). The thermal-induced grain growth of the two alloys at 1000 °C follows a law of dn − d0n = kt but the Y presence results in an increase of n from 3.46 to 3.95. This is attributed to Y segregation at the alloy grain boundaries (GBs) and Y-rich phase precipitation, which retards the GB curvature-driven grain growth thermodynamically by a solute drag effect and kinetically by second-phase pinning effect, respectively. Moreover, the Y-free alloy grains grow much faster in air than in Ar, because the surface oxidation in air generates additional tensile stresses in the alloy which facilitate the GB mobility. The Y-containing alloy nanograins remain similar in size during heating in air and in Ar, plausibly due to the formation of more Y-rich oxide particles which hinder the GB mobility through the Zener pinning effect.
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