Fatigue Study of a Zr-Ti-Ni-Cu-Be Bulk Metallic Glass
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Fatigue Study of a Zr-Ti-Ni-Cu-Be Bulk Metallic Glass G. Y. Wang1, P. K. Liaw1, A. Peker2, B. Yang1, M. L. Benson1, W. Yuan1, W. H. Peter1, L. Huang1, M. Freels1, R. A. Buchanan1, C. T. Liu3, and C. R. Brooks1 1 Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996, USA. 2 LiquidMetal Technologies, Inc., Lake Forest, CA 92630, USA. 3 Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA ABSTRACT High-cycle fatigue (HCF) studies were performed on zirconium (Zr)-based bulk metallic glasses (BMGs): Zr41.2Ti13.8Ni10Cu12.5Be22.5, in atomic percent. The HCF experiments were conducted using an electrohydraulic machine at a frequency of 10 Hz with a R ratio of 0.1 and under tension-tension loading, where R = σmin./σmax., where σmin. and σmax. are the applied minimum and maximum stresses, respectively. The test environment was air. A high-speed and high-sensitivity thermographic-infrared (IR) imaging system has been used for nondestructive evaluation of temperature evolution during fatigue testing of BMGs. Limited temperature evolution was observed during fatigue. However, no sparking phenomenon was observed at the final moment of fracture of this BMG. At high stress levels (σmax. > 864 MPa), the fatigue lives of Batch 59 are longer than those of Batch 94 due to the presence of oxides in Batch 94. Moreover, the fatigue-endurance limit of Batch 59 (703 MPa) is somewhat greater than that of Bath 94 (615 MPa) in air. The fatigue-endurance limit of Ti-6-4 is greater than this BMG, but Al 7075 has the lowest fatigue life. The vein pattern with a melted appearance were observed in the apparent melting region. The fracture morphology indicates that fatigue cracks initiate from some defects. INTRODUCTION Since the discovery in 1960 by rapid quenching of a Au80Si20 (in atomic percent) liquid [1], metallic glasses have been extensively investigated as potentially attractive structural materials because of their high strength (> 2 GPa), bend ductility; high wear resistance, and high corrosion resistance [2-4]. After the development of BMGs during the early 1990s [5-7], several interesting multicomponent BMGs, such as Zr-Al-Ni [6], Zr-Al-Cu-Ni [7], and Zr-Ti-Cu-Ni-Be [5], have been discovered, which exhibit exceptional glass-forming abilities. Peker and Johnson [5] reported that the Zr-Ti-Cu-Ni-Be BMGs forms glass at cooling rates of less than 10 K/s. Large fully amorphous rods up to 14 mm in diameter could be fabricated. The first commercial alloy, Zr41.2Ti13.8Cu12.5Ni10Be22.5 (in atomic percent), also known by its trade name VITRELOY, is now being used to fabricate golf-club heads because of its high strength-to-stiffness ratio [8, 9]. The high yield stress and the high strength to density ratio of this bulk-metallic glass make the material an excellent candidate for structural applications. Research
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on its casting ability [5], viscosity [10], kinetics [11, 12], crystallization [13], corrosion resistance [14], mechanical strength [15, 16]
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