Time resolvedin-situsynchrotron radiation diffraction investigation of grain-growth kinetics in magnetic nanocomposites

Nanocrystalline powders with nominal composition Co42Fe22Sm22Nb7B4Cu2Ag1 were synthesized by high-energy ball-milling. In the as-milled state, the alloy specimens consist of nanocrystalline α-(Fe,Co). The formation of hard magnetic Sm2Co17 or Sm2Fe17 phases within the surrounding (Fe,Co) matrix during continuous heating was followed by in- situ X-ray diffraction experiments performed at the HASYLAB/DESY synchrotron radiation facility in Hamburg, Germany. The hard magnetic Sm2Co17 nanocrystalline phase forms at temperatures near to 800°C. The temperature evolution of the grain-size distribution was obtained from the integral breadth double-Voigt analysis of the broadening of the (Fe,Co)- matrix X-ray diffraction lines. The kinetics of microstructure coarsening seems to be influ- enced by grain boundary pinning (drag) effects correlated with the formation of a two-phase microstructure.