Critical serrated flow features during nanoindentation in La-based bulk metallic glasses

Wei Peng1), Taihua Zhang2), Yuan Liu1), Lei Li1), and Bingchen Wei1) 1) National Microgravity Laboratory, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China 2) State Key Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China

摘 要：La57.6Al17.5（Cu,Ni）24.9 and La64Al14（Cu,Ni）22 bulk metallic glasses （BMGs） were prepared by copper-mould casting method. Plastic deformation behavior of the two BMGs at various loading rates was studied by nanoindentation. The results showed that the La57.6Al17.5（Cu,Ni）24.9 BMG with a glass transition temperature of 423 K exhibited prominent serrated flow at low loading rates, whereas less pronounced serrated flow at high rates during nanoindentation. In contrast, the La64Al14（Cu,Ni）22 BMG with a glass transition temperature of 401 K exhibited prominent serrated flow at high loading rates. The different rate dependency of serrated flow in the two La-based BMGs is related to the different glass transition temperature, and consequently the degree of viscous flow during indentation at room temperature. A smoother flow occurs in the alloy with relatively lower glass transition temperature, due to the relaxation of stress concentration.

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