| Summary: | 博士 === 國立中央大學 === 機械工程學系 === 102 === The (Zr48Cu36Al8Ag8)99.25Si0.75-based bulk metallic glass composite (BMGc) rods ex situ dispersed with Ta particles (with a diameter of 2–4 mm) have been successfully fabricated by suction casting and characterized. These Ta-added BMGCs exhibit similar thermal properties in comparison with its base alloy counterpart, with relatively high glass forming ability (GFA). The results of compression test show that a superior mechanical performance with up to 22% compressive plastic strain, 1800 MPa yield strength and 1850 MPa fracture strength at room temperature can be obtained for the 2 mm diameter rod of the ZrCubased BMGc with 10 vol.% Ta particles. These ex situ dispersed Ta particles (20±8 µm) would arrange as semi-uniform confinement zones to restrict the shear band propagation. In addition, for a given Ta particle size, higher volume fraction particles would lead to more interfacial areas, shorter inter-particle spacings, smaller confinement zone sizes than the smaller volume fraction particles, and results in presenting larger compression plasticity.
The Zr47.3Cu32Al8Ag8Ta4Si0.7–based bulk metallic glass composites (BMGCs) rods (with a diameter of 2 ~ 4 mm) containing different volume fractions (Vf) of ex-situ dispersed micro-sized Ta particles have been successfully fabricated by suction casting and characterized. These BMGCs with ex-situ added Ta exhibit similar thermal properties in comparison with its base alloy counterpart, with relatively high glass forming ability (GFA). The results of compression test show that a superior mechanical performance with more than 25% compressive plastic strain and 1800 MPa fracture strength at room temperature can be obtained for the 2 mm diameter rod of the ZrCu-based BMGc ex-situ added 6 and 9 vol% Ta particles, respectively. The homogeneous distributed Ta particles (5-30 µm) would arrange as semi-uniform confinement zones to restrict the shear band propagation. In addition, for a given Ta particle size, higher volume fraction particles would lead to shorter inter-particle spacings, smaller confinement zone sizes than the smaller volume fraction particles, and results in presenting larger compression plasticity. Therefore, the inter-particle free spacing, as well as the confinement zone size (mean free path of shear bands), is apparently the controlling factor in affecting the plasticity of BMGCs.
The thermoplastic deformation behavior of a Zr47.3Cu32Al8Ag8Ta4Si0.7-based bulk metallic glass composite (BMGC) is studied using thermal mechanical analyzer (TMA) and high temperature compression test in the supercooled liquid (SCL) region. The deformation behavior of the Zr47.3Cu32Al8Ag8Ta4Si0.7-based BMGC rod is investigated using TMA under compression at different strain rates (5×10−2 to 5×10−1 s−1) and at different temperatures above the onset temperature of viscous-flow (~740 to 764 K) in the SCL region. It is observed that, at a constant strain rate of 5×10−2 s−1, the flow stress decreases with increasing temperature and reaches a relatively low value about 76 MPa at 764 K. In parallel, the value of flow stress increases with increasing strain rate at the same testing temperature. A satisfactory thermoplastic forming ability of the Zr47.3Cu32Al8Ag8Ta4Si0.7-based BMGC in the SCL region is demonstrated by imprinting the hologram pattern.
A series of open-cell bulk metallic glass foams (BMGFs) with different porosity content from 46% to 75% were successfully fabricated by a space holder technique. Morphologies of the foam, the amorphous nature and mechanical properties were systematically investigated by a combination of scanning electron microscope (SEM), X-ray diffraction (XRD), differential scanning carlorimetry (DSC), and compression test. The BMGFs possess Young's moduli ranging from 4 to 21 GPa and yield strength within 65–231 MPa, matching well with the moduli as well as yield strength of human bones and the predictions from theoretical models. These BMGFs are promising for bio-implant application without significant stress shielding effect.
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