Effect of Ag addition on the enhancement of thermal and mechanical properties of Cu-Zr-Al bulk metallic glasses

• Main Authors: Tsan-Man Chung, 鍾璨蔓
• Other Authors: Pei-Ju Hsieh
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/20889028337379240950

碩士 === 義守大學 === 材料科學與工程學系 === 102 === Since the development of amorphous alloys, most scholars using Au, Pd and other more expensive metal elements as the substrate. In order to reduce costs and improve usability, scholars began to develop the Cu-based amorphous alloys, with lower cost and good mechanical properties, especially for Cu-Zr-based amorphous alloy with a deep eutectic point in Cu50Zr50 alloy system, it can easily formed an amorphous alloy in the low temperature. Therefore, Cu50Zr43Al7 alloy with high glass forming ability were be used at the base alloy in this experiment. Replace Cu elements by Ag element. Pure Ag element are selected to partially substitute Cu element to form Cu50-xZr43Al7Agx (x=0, 3, 4, 5, 6) bulk metallic glasses (BMGs) in this research. According to the literature, the adding of Ag elements can effectively enhance the thermal properties and the mechanical properties of amorphous alloys. The BMG specimens were be prepared by the use of arc-melting and injection casting process. The effect of Ag addition on the vitrification, thermal and mechanical properties of Cu-Zr-Al-Ag amorphous alloys were studied here. BMG specimens were examined by X-ray diffractometer (XRD), differential scanning calorimeter (DSC), Vickers hardness tester, material test system (MTS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results revealed that the Cu50-xZr43Al7Agx alloy systems were formed in amorphous state in this study. The glass transition temperature (Tg) and the liquidus temperature (Tl) of Cu-Zr-Al alloy decreased with adding of Ag. Hence the supercooled liquid region (Tx) and  (=Tx/(Tg+Tl)) Cu45Zr43Al7Ag5 alloy increased to 76K and 0.425, respectively. It means that the enhancement of the thermal stability and glass forming ability of Cu-Zr-Al-Ag BMG alloys with adding of Ag. The result of room temperature compressive fracture strength and strain measured from Cu47Zr43Al7Ag3 was of about 2191 MPa and 2.0%. Dense dispersion of vein pattern on the fracture surface of Cu47Zr43Al7Ag3 BMG specimen via compressive test was be observed, indicating a typical ductile fracture behavior and the improved of plasticity of alloys with minor addition of Ag. In the Cu47Zr43Al7Ag3 alloy, there were 4~10 nm nanocrystalline phase uniformly distributed in the substrate. This is the reason that the strength and plastic strain of the alloy to be enhanced here.