The Influence of Short-Term Isothermal Annealing on Changes in the Surface and the Physical and Chemical Properties of Amorphous Metal Alloy Al87Y4Gd1Ni4Fe4

This study investigates the effect of short-term isothermal annealing at 647 ± 1 K for 5 min on the surface state, electrochemical response, and tribological behavior of the Al87Y4Gd1Ni4Fe4 amorphous alloy. Scanning Kelvin probe measurements revealed a pronounced shift in the contact potential difference and a more spatially coherent distribution of CPD after annealing, indicating substantial modification of the surface electronic state. XPS analysis showed that the relative contribution of oxidized Al increased from approximately 84.4% to 92.9%, whereas the contribution of non-oxide Al species decreased from approximately 15.6% to 7.1%. At the same time, the total surface oxygen concentration decreased and yttrium became enriched in the near-surface region, demonstrating a redistribution of surface chemical states rather than a simple increase in oxidation. Annealing caused only minor changes in surface roughness but markedly improved wear performance: the specific wear rate decreased from 1.917 × 10−3 to 1.234 × 10−3 mm3/(N·m) (approximately 36%), while the maximum wear-track depth decreased from 35.8 to 8.55 μm. In contrast, electrochemical impedance spectroscopy revealed deterioration of the protective properties of the surface layer. The passive-film resistance decreased from 7845 to 4335 Ω·cm2, the charge-transfer resistance from 8692 to 5262 Ω·cm2, and the double-layer CPE exponent ndl from 0.91 to 0.74, indicating increased electrochemical heterogeneity of the interface. Thus, short-term annealing produces a distinct functional trade-off: it substantially improves the tribological performance of the Al87Y4Gd1Ni4Fe4 alloy while simultaneously reducing the effectiveness of its electrochemical surface barrier.