探討不同結晶率對鋯鋁鈷塊狀非晶質合金機械性質之影響;Study on the Mechanical and Corrosion Properties of the Partial Crystallized Zr54Al17Co29 Bulk Metallic Glass

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Title:	探討不同結晶率對鋯鋁鈷塊狀非晶質合金機械性質之影響;Study on the Mechanical and Corrosion Properties of the Partial Crystallized Zr54Al17Co29 Bulk Metallic Glass
Authors:	羅彥達;Pradana,Yanuar Rohmat Aji
Contributors:	機械工程學系
Keywords:	鋯鋁鈷金屬玻璃;恆溫熱處理;奈米晶;機械性質;耐腐蝕;Zr54Al17Co29 BMG;isothermal annealing;nanocrystal;mechanical properties;corrosion resistance
Date:	2016-07-28
Issue Date:	2016-10-13 14:53:48 (UTC+8)
Publisher:	國立中央大學
Abstract:	近年來，由於金屬玻璃具有優異的機械性能與抗菌特性，被嘗試應用於生醫器械與駐植物上。雖然添加銅、鎳或鈹可以提升鋯基金屬玻璃合金之玻璃形成能力，但是，本研究避免使用對人體有害的元素，選擇低細胞毒性的鋯鋁鈷合金系統，探討不同結晶率鋯鋁鈷金屬玻璃樣品之機械性質與耐腐蝕性質。以電弧熔煉與真空吸鑄製備直徑2, 3 與4 mm鋯鋁鈷金屬玻璃棒材，初步以X光繞射檢測其非晶性分析，在低角度（30°~50°）呈現非晶質合金典型的寬廣繞射鋒；以DSC量測後再分析其特徵溫度，鋯鋁鈷金屬玻璃之玻璃轉換溫度、結晶溫度與過冷液相區間分別為：742、794與52 K，且其活化能為：233與253 kJ mol-1(第一與第二峰值)。在過冷液相區間進行恆溫熱處理，製備結晶率為：6.6、14.5、19.8、25.5、31.5、36.4與40.1%樣品。在機械性質方面，隨著結晶率上升硬度亦呈現上升趨勢，硬度結果落在540 ± 5到575 ± 5之間；壓縮測試結果顯示結晶率6.6%的樣品具有最優異的拉伸強度與塑性變形，分別為：2160 ± 110 MPa 與 4.7 ± 0.2%，相較於未經熱處理樣品其拉伸強度與塑性變形僅有：2130 ± 75 MPa 與 2.2 ± 1.6%，這是由於基地內結晶顆粒阻擋了shear band 的前進，同時，在結晶率6.6%樣品的破裂面上可以觀察到許多葉脈紋的生成，佐證此一論點。以恆電位法分析鋯鋁鈷樣品的耐腐蝕性能，6.6%結晶率的樣品呈現與316不鏽鋼相似的結果。根據本研究的結果，評估鋯鋁鈷金屬玻璃的確可以被應用在生醫器械上。 ;Development of metallic materials is recently essential for biomedical application. Therefore, Zr-based bulk metallic glasses become favorable due to their attractive properties. Zr-Al-Co BMGs, as low-toxic material, having less possibility to harm the human body compared with other Cu-, Ni-, and Be-containing Zr-based BMGs, however, most of them show the limited ductility. The structural modification through partial crystallization on Zr54Al17Co29 BMG was obtained by isothermal annealing and the correlation with the mechanical and corrosion resistance have been investigated. Zr54Al17Co29 BMG rod with diameter of 2, 3, and 4 mm was successfully fabricated by arc melting and suction casting, afterwards, the amorphous properties were examined by XRD, SEM, and DSC. A single broad peak of XRD pattern, good chemical homogeneity, and the information of Tg, Tx, and ∆Tx (742, 794, and 52 K) were obtained from the analyses, indicating the sample was fully amorphous. By Kissinger plots, activation energies of crystallization for the first and second exothermic peak are determined to be 233 and 253 kJ mol-1. The isothermal annealing was conducted at the temperature within SCL region for different times that was determined by JMA isothermal analysis in order to variate sample crystallinities. TEM analysis reveals that ZrCo2Al crystal phase with size of 10 nm is observed from sample with 40.1% crystallinity. Mechanical properties of as-cast and partially crystallized samples containing 6.6; 14.5; 19.8; 25.5; 31.5; 36.4; and 40.1% crystallinities were studied by hardness and compression test. The results reveal that the hardness slightly increases with increasing the crystallinity, in range 540 ± 5 to 575 ± 5 Hv. However, the results of compression test show a different trend, yield strength and plastic strain are significantly improved when the sample reaches 6.6% crystallinity. Afterwards, the deteriorating effect of excess nanocrystal contents for the sample with higher crystallinity on the plastic strain was observed while yield strength remains constant. The sample containing 6.6% crystallinity shows the remarkable improvement of yield strength and plastic strain (2160 ± 110 MPa and 4.7 ± 0.2%), higher than the as-cast counterparts (2130 ± 75 MPa and 2.2 ± 1.6%). This improvement is attributed to the optimum nanocrystal content to restrict the shear bands propagation accompanied without any free volume reduction effect due to short annealing time. In addition, the fracture surface morphology of the sample with 6.6% crystallinity shows the mixed vein and river-like pattern, indicating strong interaction between shear bands and nanocrystals. Moreover, the as-cast and partially crystallized with 6.6% crystallinity samples show similar corrosion resistance and comparable with the 316 stainless steel by potentiodynamic polarization test. In summary, the Zr54Al17Co29 BMG with 6.6% crystallinity is believed as promising candidate for biomaterial applications.
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