Yielding and intrinsic plasticity of Ti–Zr–Ni–Cu–Be bulk metallic glass

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• 作者：J. Fornell ; A. Concustell ; S. Suriñ ; ach ; W.H. Li ; N. Cuadrado ; A. Gebert ; M.D. Baró ; J. Sort
• 关键词：A. Yield condition ; B. Elastic– ; plastic material ; B. Metallic glass material ; C. Mechanical testing ; C. Nanoindentation
• 刊名：International Journal of Plasticity
• 出版年：2009
• 出版时间：August 2009
• 年：2009
• 卷：25
• 期：8
• 页码：1540-1559
• 全文大小：649 K

文摘

Bulk metallic glass with composition Ti₄₀Zr₂₅Ni₈Cu₉Be₁₈ exhibits considerably high compressive yield stress, significant plasticity (with a concomitant vein-like fracture morphology) and relatively low density. Yielding and intrinsic plasticity of this alloy are discussed in terms of its thermal and elastic properties. An influence of normal stresses acting on the shear plane is evidenced by: (i) the fracture angle (<45°) and (ii) finite-element simulations of nanoindentation curves, which require the use of a specific yield criterion, sensitive to local normal stresses acting on the shear plane, to properly match the experimental data. The ratio between hardness and compressive yield strength (constraint factor) is analyzed in terms of several models and is best adjusted using a modified expanding cavity model incorporating a pressure-sensitivity index defined by the Drucker–Prager yield criterion. Furthermore, comparative results from compression tests and nanoindentation reveal that deformation also causes strain softening, a phenomenon which is accompanied with the occurrence of serrated plastic flow and results in a so-called indentation size effect (ISE). A new approach to model the ISE of this metallic glass using the free volume concept is presented.