| 摘要: | 本研究中首先利用添加延性第二相阻擋剪切帶(shear band)並由墜落式急冷鑄造法製備出(Zr48Cu36Al8Ag8)99.25Si0.75之塊狀金屬玻璃複材(bulk metallic glass composite BMGc)，非晶質合金複材,其直徑為2-4mm之棒材。這些含Ta強化顆粒之非晶質合金複材具有著和基材相似的熱性質且具高的GFA(glass forming ability)。ZrCu基(BMG)添加10 vol.% Ta顆粒在壓縮試驗中(直徑2mm)也表現出22%真實塑性變形量，降伏應力為1800MPa,破壞強度達1850MPa(室溫下)；外添加之Ta顆粒均勻分布於基材中,且顆粒間之平均間距為20±8 µm，以此來限制或阻擋shear band之傳遞。此外隨著Ta添加量增加，Ta顆粒之間的間距更短、Ta塑性區範圍更大會使得ZrCu 基BMGc塑性變形能力提升。
為了結合奈米級Ta析出相和微米級Ta顆粒之韌化效用，接著利用內析出及外添加Ta顆粒的方式成功地將Zr47.3Cu32Al8Ag8Ta4Si0.7成份之基材以墜落式鑄造法製備出包含奈米級Ta析出相及微米級Ta顆粒之金屬玻璃複材(直徑2~4mm)，這些具奈米及微米級Ta顆粒之塊狀金屬玻璃複材具有和基材相似的熱性質及高的玻璃形成能力(glass forming ability,GFA)。室溫下ZrCu基BMGc含外添加6和9 vol.% Ta顆粒在壓縮試驗中(直徑2mm)也表現出超過25%真實塑性變形量,降伏應力約為1800MPa。均勻且較大之Ta(5-30µm)添加量(分布量)會限制剪切帶之傳遞，而奈米級較小的Ta塑性區也同時提升鋯銅基塊狀金屬玻璃複材之塑性變形量，因此延性顆粒間之間距及塑性區大小是BMGc提升塑性變形量之關鍵因素。
本研究也針對金屬玻璃複材之熱塑加工性進行探討，選用Zr47.3Cu32Al8Ag8Ta4Si0.7基材成份之塊狀金屬玻璃為試驗基材，並利用TMA在不同應變速率及不同溫度下（〜740至764 K）(5×10−2 to 5×10−1 s−1)研究其過冷液相區之熱塑性變形性質及流變應力。結果顯示在5×10−1 s−1應變速率下，該金屬玻璃複材之流變應力隨熱壓溫度升高而降低，且在764K時達到一個相對較低的流變應力值約為76MPa。同時在相同熱壓溫度下，其流變應力也會隨應變速率增加而增加。此外，透過複印精細度為奈米級之雷射貼紙實驗，証實了Zr47.3Cu32Al8Ag8Ta4Si0.7塊狀金屬玻璃複材於其過冷液相區也具備優良了的奈米級複印能力。
最後本研究利用金屬玻璃特有之過冷液相區超塑成形特性，並利用熱塑成型之粉冶金製程，成功地製備出含46~75%不同孔隙率之鋯基塊狀金屬多孔材（bulk metallic glass foam, BMGFs），並利用XRD及SEM和DSC來觀察其非晶性及孔洞大小和形態，研究結果發現此系列鋯基塊狀金屬多孔材（BMGFs）之楊氏系數範圍為4~21GPa，降伏應力在65~231MPa之間；楊氏系數和降伏應力都符合人體骨骼之機械性質。並從多孔理論模型預測中看出與降伏強度和楊氏系數和預測結果相符；可用做生物植入材並避免應力遮蔽效應。
;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. |
