Microstructure evolution of nano-crystalline HITPERM and NANOPERM alloys: Insight fromin-situsynchrotron radiation experiments

Abstract

The properties of nanocrystalline materials differ from the ones of their coarse- grained counterparts. Significant changes of the phase diagrams were also recently reported for various nanomaterials. Thermomechanical processing routes - with or without pressure application - employed to obtain bulk nanostructured solids from nanocrystalline powders control the microstructural features down to the nanoscale and thus determine the final nanomaterial properties. Modern in-situ X-ray diffraction experiments provide effective tools for the observation and engineering of the microstructure in nanomaterials. Time-resolved in-situ synchrotron radiation diffraction experiments were here used to monitor the evolution of the weighted column-length distributions and microstrain at specimen-relevant scales during heating of nanocrystalline HITPERM and NANOPERM alloys. Diffraction line pro- file analysis methods were applied to observe the grain growth kinetics in these Fe(Co)-Zr- B-Cu nanostructured alloys. The retention of their excellent soft magnetic properties in par- ticular at high temperature depends on the ability to supress anomalous grain growth.