Structure and Properties of the Melt-SpunZr–(Al)–Ni–Cr–Ag Alloys

The structure, mechanical and electrical properties of Zr-based melt-spun Zr–(Al)–Ni–Cr–Ag alloys were investigated as a function of elemental composition. X-ray diffraction reveals the structural evolution from fully amorphous to nanocrystalline states, with the latter containing Zr2Ni “big-cube” (space group Fd3̄m, cF96), fcc-Zr2Ni, and β-Zr phases depending on the alloying ratio: Cr-rich compositions (≥15 at.%) stabilize β-Zr within the amorphous matrix, whereas Ag-enriched alloys promote “big-cube” phase formation. Ag atoms can replace both Zr and Ni sites in the “big-cube” lattice, yielding a (Zr,Ag)2(Ni,Ag) solid solution and highlighting its role as a structural bridge between the amorphous and crystalline states. Nanoindentation measurements show that hardness increases from 6.5 GPa in fully amorphous ribbons to 10.12 GPa in three-phase nanocrystalline composites, with an H/E ratio of ~0.08 indicating predominantly covalent bonding, and the fracture strength of the amorphous alloys is ~2 GPa, exceeding literature values for related Zr-based systems. Electrical resistivity measurements over the 4–298 K range show that most alloys deviate from Matthiessen’s rule, exhibiting a negative temperature coefficient of resistivity consistent with the Mooij correlation; the presence of the icosahedrally ordered “big-cube” phase further increases resistivity relative to fully amorphous alloys.