In situ Observation of Phase Transformation in MnAl(C) Magnetic Materials.

ABSTRACT: The phase transformation in two modes, including both displacive and massive growth of ?-phase from ?-MnAl(C), was observed by in situ transmission electron microscopy. The exact temperature range for different phase transformation modes was determined by magnetic measurements. The displacive growth of ??? in Mn₅₄Al₄₆ (or Mn₅₄Al₄₆C_2.44) occurs at temperatures below 650 K (or 766 K), above which both modes coexist. One-third or less of the ?-phase can be transformed into ?-phase via displacive mode while the remaining two-thirds or more via massive mode. In bulk ?-phase, most ?-nanocrystals formed via displacive mode are distributed in the matrix of large ?-grains that formed via massive mode. The typical massive growth rate of the ?-phase is 8-60 nm/s, while the displacive growth rate is low. A more complete understanding of the ??? phase transformations in the MnAl-based magnets was provided in this work, based on which the annealing process for ??? was optimized and thus high purity ?-phase with high saturation magnetization was obtained.

SUBMITTER: Si PZ 

PROVIDER: S-EPMC5615671 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature