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(73.9)Cu(1)Nb(3)Si(15.5)B(6.6) and Fe(81.2)Co(4)Si(0.5)B(9.5)P(4)Cu(0.8) have been investigated and compared. While for Fe(73.9)Cu(1)Nb(3)Si(15.5)B(6.6), HPT processing allows us to extend the known consolidation and deformation ranges, HPT processing of Fe(81.2)Co(4)Si(0.5)B(9.5)P(4)Cu(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(81.2)Co(4)Si(0.5)B(9.5)P(4)Cu(0.8) exhibits HPT-induced crystallization phenomena, while Fe(73.9)Cu(1)Nb(3)Si(15.5)B(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.