Nanocrystallization in spark plasma sintered Fe_(48)Cr_(15)Mo_(14)Y_2C_(15)B_6 bulk amorphous alloy

摘要

Spark plasma sintering (SPS) is evolving as an attractive process for the processing of multi-component Fe-based bulk amorphous alloys and their in-situ nanocomposites with controlled primary nanocrystallization. Extended Q-range small angle neutron scattering (EQ-SANS) analysis, complemented by x-ray diffraction and transmission electron microscopy, was performed to characterize nanocrystallization behavior of SPS sintered Fe-based bulk amorphous alloys. The SANS experiments show significant scattering for the samples sintered in the supercooled region indicating local structural/compositional changes associated with the profuse nucleation of nanoclusters (～4nm). For the samples spark plasma sintered near and above crystallization temperature (＞653 ℃), the SANS data show the formation of interference maximum indicating the formation and growth of (Fe,Cr)_(23)C_6 crystallites. The SANS data also indicate the evolution of bimodal crystallite distribution at higher sintering temperatures (above T_(x1)). The growth of primary nanocrystallites results in impingement of concentration gradient fields (soft impingement effect), leading to non-random nucleation of crystallites near the primary crystallization.