Enhancing fatigue wear resistance of a bulk metallic glass via introducing phase separation: A micro-impact test analysis

Bulk metallic glasses (BMGs) are potential candidate materials for numerous structural applications. However, this class of materials has a major limitation for engineering applications due to their inferior resistance to fatigue wear. In present work, a novel micro-scale repetitive impact test was utilized for fatigue testing of ZrCu-based BMGs (Zr_63.6-xCu₁₈Ni_10.4Al₈Fe_x, x = 0, 3, 5 at.%), and specific attention was paid to the micro-alloying effect on wear resistance. Transmission electron microscopy of as-cast Zr_58.6Cu₁₈Ni_10.4Al₈Fe₅ revealed amorphous structure with the formation of a second glassy phase of few nanometers in diameter. Although these structural changes have minor effects on hardness and modulus, they have a substantial influence on fatigue wear resistance. Phase separation was found to promote numerous shear bands, which induced strain hardening, and improved the crack resistance. Consequently, all these features are considered to contribute the improved wear resistance. On the contrary, a monolithic glass without Fe addition lacks any microstructural features that can provide means for the local arrest of shear bands and incipient fatigue cracks. These findings improve the understanding of the impact fatigue mechanisms and provide suggestions for the future design of BMGs with excellent wear performance.