Free Volume Redistribution in Amorphous Interfaces During Relaxation of a Spray Deposited Amorphous Alloy

Amorphous alloys have been widely recognized as potential engineering structural materials due to their near-theoretical mechanical strength and enhanced wear and corrosion resistance, which is derived from an atomic arrangement lacking long range symmetry. However, the lack of intrinsic strain hardening mechanisms upon yielding results in strain localizing into shear bands, leading to brittle fracture in unconstrained modes of loading. Exploiting free volume modulations to promote a more homogeneous plastic response has been a central theme in the development of bulk metallic glasses, employing both intrinsic and extrinsic approaches to introduce structural heterogeneities within the matrix and have led to the development of novel interface-engineered amorphous alloys. Here, we employ synchrotron scattering techniques to quantify the short-to-medium range amorphous atomic network of an Fe-based bulk metallic glass synthesized through additive spray deposition and annealed up to the glass transition temperature. Observed variations in atomic nearest neighbor bonding are then connected to atomistic simulations of alloy nanoglasses to elucidate the effects of amorphous interfaces imparted through the spray deposition process on structural relaxation. The results show that annealing up to the glass transition temperature is accompanied by a global reduction in excess free volume in all samples, as expected. However, contrary to the atomized powders, the spray deposits retain excess free volume at interfacial regions between the amorphous matrix regions, which are shown to expand through free volume redistribution into adjacent particle cores during glass homogenization.