On the Phase Transformations in Cr-FeB and Fe-CrB Systems at High Temperature

The solid state interactions occurring at high temperature in the Cr-FeB and Fe-CrB systems were studied by transmission Moessbauer and X-ray diffraction techniques on samples prepared by powders carefully mixed, cold-compacted and then treated at 1000oC for times up to 16 h. In the Cr-FeB system, iron atoms liberated by the substitutional diffusion of Cr into FeB lattice preferentially destabilize the iron monoboride with formation of Cr-containing Fe2B. In the Fe-CrB system, chromium atoms liberated by the substitutional diffusion of Fe into CrB lattice interacts with iron forming an Fe-Cr metal alloy. Moreover, zones of Cr-containing FeB and Fe2B form at the contact between metal iron and chromium monoboride, and tend to disappear as iron is consumed by the alloying process.