鈦與氧化鋯介面高溫反應機構及其結構分析

Abstract

本研究探討Ti與ZrO2經1100-1550oC熱處理後介面反應的微觀結構及生成機構應。將利用EPMA、SEM/EDS、及 TEM/EDS深入分析完整瞭解不同熱處理溫度的介面微觀結構的差異性，並利用相圖Ti-Zr-O相圖，進一步探討Ti與ZrO2擴散偶介面微觀結構的演化(Microstructural Evolution)及生成機構(Formation Mechanism)。

鈦與氧化鋯擴散偶經1100℃介面反應後，層狀結構的Ti2ZrO＋α-Ti(Zr, O)在介面處生成。氧化鋯側的變化不明顯。當鈦與氧化鋯擴散偶經1300℃介面反應後，三層明顯的反應層在介面處生成，由鈦至氧化鋯側分別為層狀結構的Ti2ZrO＋α-Ti(Zr, O)、緻密的orthorhombic 結構之β'-Ti(Zr, O)及β'-Ti(Zr, O)＋c-ZrO2-x(cubic之缺氧氧化鋯)兩相共存。遠離介面處的氧化鋯側，α-Zr（hexagonal結構）與t-ZrO2-x(tetragonal之缺氧氧化鋯)共存，在冷卻過程中，α-Zr(O)會從t-ZrO2-x中析出，當α-Zr(O)析出後，O/Zr之比值就會增加。愈靠近介面，氧擴散進鈦側的量愈多，缺氧愈嚴重，其析出的α-Zr(O)量愈多。 鈦與氧化鋯擴散偶經1400℃介面反應後，四層明顯的反應層在介面處發現，依序從鈦側至氧化鋯側分別為層狀結構的Ti2ZrO＋α-Ti(Zr, O)、針狀的α-Ti(Zr, O)＋β'-Ti(Zr, O)兩相共存、緻密的β'-Ti(Zr, O)及β'-Ti(Zr, O)＋c-ZrO2-x(cubic之缺氧氧化鋯)兩相共存。冷卻過程中，針狀的α-Ti(Zr, O)從β'-Ti(Zr, O)中析出，析出方式以ledge mechanism成長，其之間有兩種方位關係：一種為[2-1-10]α-Ti // [001]β'-Ti 及 (0001)α-Ti // (100)β'-Ti，另一種為[2-1-10]α-Ti // [021]β'-Ti 及 (0001)α-Ti // (1-12)β'-Ti.。遠離介面處的氧化鋯側，發現有α-Zr(O)、lenticular t-ZrO2-x (透鏡狀之tetragonal缺氧氧化鋯氧化鋯)、twined t'-ZrO2-x及ordered 結構之cubic-ZrO2-x。

鈦與氧化鋯擴散偶經1550℃介面反應後，五層明顯的反應層在介面處發現，依序從鈦側至氧化鋯側分別為層狀結構的Ti2ZrO＋α-Ti(Zr, O)、Ti2ZrO＋α-Ti(Zr, O)＋β'-Ti(Zr, O)三相共存、針狀的α-Ti(Zr, O)＋β'-Ti(Zr, O)兩相共存、緻密的β'-Ti(Zr, O)及β'-Ti(Zr, O)＋c-ZrO2-x(cubic之缺氧氧化鋯)兩相共存。冷卻過程中，Ti2ZrO相從α-Ti中析出，高溫反應過程中，Zr與O固溶於α-Ti(Zr, O)中，當α-Ti固溶達到飽合時，即以Ti2ZrO結構析出，且析出的Ti2ZrO有兩種型態，一種為斜方晶相(orthorhombic)的層狀結構，Ti2ZrO與α-Ti的方位關係為[0001]α-Ti//[110]Ti2ZrO及(10-10)α-Ti//(1-10)Ti2ZrO；另一種為六方晶相(hexagonal)的顆粒狀結構，其方位關係為[0001]α-Ti//[0001]Ti2ZrO及(10-10)α-Ti//(10-10)Ti2ZrO。遠離介面處的氧化鋯側，發現有α-Zr(O)、lenticular t-ZrO2-x (透鏡狀之tetragonal缺氧氧化鋯氧化鋯)、twined t'-ZrO2-x及ordered 結構之cubic-ZrO2-x。

The diffusional reaction between titanium and zirconia was carried out isothermally in argon at temperatures range from 1100° to 1550°C. The distinct reaction layers between titanium and zirconia were investigated using electron probe microanalyses (EPMA), analytical scanning electron microscopy (SEM), and analytical transmission electron microscopy (TEM) both attached with an energy-dispersive spectrometer (EDS). After annealing at 1100°C/6 h, a lamellar of Ti2ZrO and α-Ti(O, Zr) phases were found in the interface, while zirconia grains did not grow conspicuously. At 1300°C, a lamellar of Ti2ZrO + α-Ti(O, Zr) and β'-Ti (Zr, O) were found in the titanium side. The α-Zr excluded from t-ZrO2-x in the zirconia side during cooling. At 1400°C, lamellar of Ti2ZrO + α-Ti(O, Zr), acicular α-Ti (O, Zr) + β'-Ti (O, Zr), and continuous β'-Ti (Zr, O) layers were found in the titanium side. The acicular α-Ti(Zr, O) was precipitated from β'-Ti(Zr, O) matrix by means of the ledge mechanism. The acicular α-Ti and the β'-Ti showed two different orientation relations: one was [2-1-10]α-Ti // [001]β'-Ti and (0001)α-Ti // (100)β'-Ti, and the other was [2-1-10]α-Ti // [021]β'-Ti and (0001)α-Ti // (1-12)β'-Ti. After annealing at 1550°C, four layers in a sequence of Ti2ZrO + α-Ti(O, Zr), Ti2ZrO + α-Ti(O, Zr) + β'-Ti (O, Zr), acicular α-Ti (O, Zr) + β'-Ti (O, Zr), and continuous β'-Ti (Zr, O) were formed in the titanium side after cooling. The lamellar and the spherical Ti2ZrO, which were orthorhombic and hexagonal, respectively, were found. The spherical hexagonal Ti2ZrO was an ordered structure, with zirconium and oxygen occupying substitutional and interstitial sites, respectively. The orientation relations between α-Ti and the lamellae orthorhombic Ti2ZrO were determined to be [0001]α-Ti // [110]Ti2ZrO and (10-10)α-Ti // (1-10)Ti2ZrO; meanwhile those between the α-Ti and the spherical hexagonal Ti2ZrO were [0001] α-Ti // [0001]Ti2ZrO and (10-1 0)α-Ti // (10-10)Ti2ZrO. In the zirconia side, when held above 1400°C, two reaction layers were found: near the original interface, β'-Ti coexisted with fine spherical c-ZrO2-x and Chinese-script-like c-ZrO2-x, which dissolved a significant amount of Y2O3 in solid solution; further away from the original interface, the coarsened intergranular α-Zr was excluded from metastable ZrO2-x, resulting in the lenticular t-ZrO2-x and ordered c-ZrO2-x. The ordered c-ZrO2-x was identified by the 1/5{113} superlattice reflections of its electron diffraction patterns. The microstructural developments and reaction mechanisms in the Ti/ZrO2 diffusion couples annealed for various temperatures were described by the aid of the Ti-Zr-O ternary phase diagram.