Can Severe Plastic Deformation Tune Nanocrystallization in Fe-Based Metallic Glasses?

The effects of severe plastic deformation (SPD) by means of high-pressure torsion (HPT) on the structural properties of the two iron-based metallic glasses Fe 73.9Cu 1Nb 3Si 15.5B 6.6 and Fe 81.2Co 4Si 0.5B 9.5P 4Cu 0.8 have been investigated and compared. While for Fe 73.9Cu 1Nb 3Si 15.5B 6.6, HPT processing allows us to extend the known consolidation and deformation ranges, HPT processing of Fe 81.2Co 4Si 0.5B 9.5P 4Cu 0.8 for the first time ever achieves consolidation and deformation with a minimum number of cracks. Using numerous analyses such as X-ray diffraction, dynamic mechanical analyses, and differential scanning calorimetry, as well as optical and transmission electron microscopy, clearly reveals that Fe 81.2Co 4Si 0.5B 9.5P 4Cu 0.8 exhibits HPT-induced crystallization phenomena, while Fe 73.9Cu 1Nb 3Si 15.5B 6.6 does not crystallize even at the highest HPT-deformation degrees applied. The reasons for these findings are discussed in terms of differences in the deformation energies expended, and the number and composition of the individual crystalline phases formed. The results appear promising for obtaining improved magnetic properties of glassy alloys without additional thermal treatment.