Tension-Tension-Fatigue Behaviors of a Zr-Based Bulk-Metallic-Glass-Matrix Composite
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lk-metallic glasses (BMGs) exhibit superior properties at ambient temperature, such as high strengths, large elastic limits, and excellent corrosion and wear resistance, which renders them potential candidates as structural engineering materials.[1] However, the localized shear banding upon loading induces the catastrophic failure, restricting the practical engineering applications. Recently, newly developed in-situ bulkmetallic-glass-matrix composites (BMGMCs), including the ductile dendrites within the glass matrix, demonstrate significantly improved toughness, especially with the tensile ductility, by tuning the compositions[2,3] or tailoring the microstructures.[4,5] Microscopically, the plastic-deformation mechanism of in-situ BMGMCs is characterized by the multiplication of shear bands, caused by the impediment of crystalline phases to the operation of shear bands.[2–4] The possible micromechanism of the plastic deformation could be the severe lattice distortion and local amorphization in the dendrites, as well as pileups of dislocations close to the interface between the dendrites and the glass matrix.[6] J.W. QIAO, Researcher, is with the College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, P.R. China. Contact e-mail: [email protected] S.G. MA, Doctoral Student, and Y. ZHANG, Professor, are with the State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, P.R. China. G.Y. WANG and F. JIANG, Researchers, and P.K. LIAW, Professor, are with the Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996-2200. Manuscript submitted December 28, 2010. Article published online July 6, 2011 2530—VOLUME 42A, SEPTEMBER 2011
As a result, an improved plasticity is available for BMGMCs. The fatigue behavior is a very important characteristic for applications of structural materials. Components are frequently bearing cyclic loads, with the load being time dependent, but repetitive, and almost 90 pct of the service failure is caused by the fatigue fracture.[7] However, very limited studies[8–11] are focused on the fatigue behaviors of BMGMCs. In this study, the highcycle fatigue behaviors of a Zr-based BMGMC with the composition of Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 in atomic percent are characterized by the tension-tension fatigue, and the relevant fatigue-deformation mechanism is explored. The Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 BMGMC was prepared in a cylinder shape with a diameter of ~5 mm, fabricated by the copper-mold-suction casting. The detailed procedures of the fabrication can be found in Reference 6. The cross section of the as-cast sample was investigated using scanning electron microscopy (SEM). The rod-shaped cast samples were machined into buttonhead fatigue specimens with a notch. The geometry of the notched samples and the setup for the tension-tension fatigue can be found elsewhere.[12] The stress-concentration factor is 1.5 at the notched section.[13] Samples were teste
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