| 摘要: | 由於金屬玻璃其獨特的優良性質，使其成為各國近年來炙手可熱並且積極開發的新興材料之一。但除了良好的機械性質之外，金屬玻璃缺乏塑性此一缺點大大限制了其可應用的範圍，因此許多進階研究利用複合材料的觀念，以內析出(In-situ)或是外添加(Ex-situ)的方式使金屬玻璃基地內產生第二相(Second phase)，能有效地改善此一缺點。
本實驗設計分別利用傾倒式鑄造(Tilt-casting)、吸鑄式鑄造(Suction-casting)、射出成型(Injection)以及淬火(Quench)四種不同製程製備Zr47.5Cu47.5Al5與Zr48Cu47.5Al4Co0.5不同尺寸(直徑2~4mm)非晶質合金圓柱複材，先觀察由上述四種不同製程所製作之金屬玻璃複材中In-situ的體心立方之鋯銅相(BCC-ZrCu phase)及孔洞之分布情形，然後進行單軸向壓縮測試，同時並計算不同製備方式所得樣品之雷諾數(Reynolds number)與其金相結構關係，進一步釐清析出相及孔洞之尺寸及分布對其機械性質之影響。
單軸向壓縮測試結果顯示，所有製程之2mm棒材均較其他尺寸之棒材有較佳的塑性表現，而其中以傾倒式鑄造之Zr48Cu47.5Al4Co0.5 2mm棒材具有最佳表現，其塑性變形量可達16%，經由雷諾數的計算可得知，以傾倒式鑄造的雷諾數值較低，流體流動狀態較接近層流，表示流體分層流動，互不混合，因此，相較於其他製程，傾倒式鑄造製備的樣品非晶質合金基地內可以得到分布較均勻且顆粒尺寸較大的B2相，同時由於傾倒式鑄造的試片內部缺陷較少，因此具有較好的塑性。
;Owing to the unique and excellent properties of bulk metallic glass (BMG), it has become hot-spot and attracted lots of countries to develop it actively in recent year. However, the disadvantage of metallic glass is lack of ductility, which limits the range of application. Therefore, many studies use the concept of composite materials, by using the in-situ or ex-situ approach to generate the second phase in metallic glass matrix to restrict the shear band propagation and so as to improve the plasticity of BMGC.
In this research, we use four different processes, tilt-casting, suction-casting, injection-casting, and directly quenching to make the different size (2~4mm) of Zr48Cu47.5Al4Co0.5 and Zr47.5Cu47.5Al5 BMGC rods. Using the four different processes to observe the distribution of holes and in-situ ZrCu B2 phase. The size and distribution of B2 phase and porosity were examined by optical microscopy as well as scanning electron microscopy. Then the mechanical properties of these BMGC rods were obtained by uniaxial compression test. In addition, the Reynolds number of each process was also estimated to figure out the formation of B2 second phase, and relate to its mechanical performance.
After uniaxial compression testing, the 2mm diameter BMGC rods made from each casting process have the better plasticity than the other diameter samples. Among all the 2mm-diameter samples, the tilt casting 2mm-diameter Zr48Cu47.5Al4Co0.5 sample present the best mechanical performance, it can reach 16% plastic deformation. Through the calculation of Reynolds number, tilt-casting has lower value of Reynolds number and the fluid flow mode close to the laminar flow. Therefore, this more stable melt flow makes the formation of ZrCu B2 phase to form a larger size and more homogeneous distribution in the amorphous matrix.
In this research also use ultrasonic testing to discuss the mechanical properties of metallic glass composite rods, such as Poisson’s ratio, shear modulus and bulk modulus etc. Among the rods by tilt casting have much better mechanical performances because of much lower defects in the rods. |
