Work

Concentration threshold of yttrium addition on glass-forming ability and mechanical properties of ZrCuNiAlAg bulk metallic glass

Year: 2025

Type: article

Abstract: The influence of Yttrium (Y) microalloying on the glass-forming ability (GFA), thermal stability, microstructural evolution, and mechanical properties of a Zr55Cu29.5Ni5Al10Ag0.5 bulk metallic glass (BMG) was systematically investigated through a combination of experimental methods combined with and first-principles calculations. A distinct concentration-threshold effect was observed. Low Y additions (0.5 at.%) significantly enhanced the GFA (the critical diameter increased from 6 mm to 10 mm) and thermal stability (the supercooled liquid region ΔT widened from 35 K to 41 K), primarily attributed to Y's efficient oxygen-scavenging role. First-principles calculations revealed that Y preferentially forms Y-O short-range order with a 34.5% reduced bond length (5.15 Å), stabilizing the amorphous structure against crystallization. Concurrently, hardness, elastic modulus, and compressive yield strength peaked at 0.5 at.% Y (σ = 1783 MPa). However, higher Y concentrations (> 0.5-0.8 at.%) led to a decrease in GFA, thermal stability, and mechanical strength (σ dropped to 1713 MPa at 1.0 at.% Y). This degradation is correlates with the formation and coarsening (> 1 μm) of crystalline Y2O3 precipitates, which was confirmed by SEM/TEM. Density functional theory (DFT) calculations indicated Y2O3 is significantly stiffer than the matrix, with an elastic modulus of 109 GPa, hardness of 7.43 GPa, and compressive strength of 1783.5 MPa. However, excessive Y doping (≥ 0.8 at.%) induces coarsening of micron-scale precipitates, leading to structural heterogeneity and mechanical degradation. The study elucidates the dual role of Y: beneficial atomic-level purification and stabilization at low levels versus detrimental microstructural coarsening at higher levels, It establishes an optimal concentration of approximatiely 0.5 at.% Y and provides insights for designing high-performance RE-doped BMGs.

Source: Journal of Alloys and Compounds

DOI: 10.1016/j.jallcom.2025.183600