- 學位論文
添加Ag元素對Cu-Zr-Al非晶質合金熱性質與機械性質之影響
Effect of Ag addition on the enhancement of thermal and mechanical properties of Cu-Zr-Al bulk metallic glasses
摘要
為了降低非晶質合金之成本並提高實用性，學者們發展出成本較低且具有良好熱性質與機械性質之Cu基非晶質合金。其中以Cu-Zr基非晶質合金最受矚目，因為在Cu50Zr50合金在相圖中具有深的共晶點，因此可在較低的溫度下形成非晶質合金，其玻璃形成能力(GFA)良好。因此本實驗選用具有較佳玻璃形成能力之Cu50Zr43Al7合金作為基材，並利用Ag元素取代合金中之Cu元素，形成Cu50-xZr43Al7Agx (x=0, 3, 4, 5, 6)四元合金以作為本研究之主題。根據文獻指出，Ag元素的添加可有效提升非晶質合金之熱性質與機械性質，例如J.C. Oh研究在常溫壓縮模式下Cu43Zr43Al7Ag7非晶質合金具有高達8 %的塑性變形量，且過冷液相區間(Tx)提升至72 K[1]，因此本實驗中將探討Ag元素的添加對Cu-Zr-Al非晶質合金之玻璃形成能力、熱穩定性與機械性質的影響。 所製備出之Cu50-xZr43Al7Agx (x=0, 3, 4, 5, 6)四元合金以X光繞射儀(XRD)進行相的鑑定、示差掃描熱量計分析(DSC)進行熱性質分析、維氏硬度機和動態萬能材料試驗機(MTS)進行機械性質分析、掃描式電子顯微鏡(SEM)和穿透式電子顯微鏡(TEM)進行顯微結構分析。 實驗結果顯示，隨著Ag元素的添加，玻璃轉換溫度(Tg)及液相線溫度(Tl)由基材的731 K及1182 K降低至Cu45Zr43Al7Ag5的711 K及1142 K。因此，Cu45Zr43Al7Ag5非晶質合金之過冷液相區間(Tx)及(=Tx/(Tg+Tl)由基材之54 K及0.410分別提高至76 K及0.425，其結果表示Ag元素的添加有助於提高Cu-Zr-Al非晶質合金之玻璃形成能力與熱穩定性。 合金之硬度隨著Ag元素之添加可由基材的490.4 Hv提升至Cu47Zr43Al7Ag3的513.8 Hv。此外，Cu47Zr43Al7Ag3之常溫壓縮破壞強度與塑性應變量為2191 MPa及2.0 %，較基材高出許多。而由掃描式電子顯微鏡(SEM)觀察可發現Cu47Zr43Al7Ag3之破斷側表面呈現，發現非晶質合金典型的韌性破壞特有之剪切帶(Shear band)，該合金之破斷面上則密佈葉脈紋(Vein pattern)，顯示Ag元素的添加有助於提高Cu-Zr-Al非晶質合金之機械性質。而由穿透式電子顯微鏡(TEM)分析發現，Cu47Zr43Al7Ag3非晶質合金中有4~10 nm的奈米晶相均勻分布在基材中，導致合金受壓縮破壞時，二次及多重剪切帶之產生，因進而提升合金之破壞強度及塑性應變量。
關鍵字
none並列摘要
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.