ZrO2中相变动力学的研究.ppt

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ZrO2中相变动力学的研究.ppt

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* ZrO2 中t?m相变动力学的研究 Kinetics of t?m Transformation in ZrO2 L c t m (2680?C) (2370?C) (1170?C) c?t e11 = e22 = - 0.00878 e33 = 0.01209 t?m e11 = - 0.00149 e22 = 0.02442 e33 = 0.02386 e13 = e31 = - 0.08188 Martensitic characteristics of t?m transformation in ZrO2 Volumetric expansion 3~5% Shear strain 8% Twins Orientation relationships (100)t // (100)m [001]t // [001]m Habit plane (010)m (106)m (671)m Surface relief Self-catalytic Stabilizers to ZrO2 Y2O3, MgO, CeO2, CaO, etc. Structures: ZrO2 + 0mol% Y2O3 m ZrO2 + 2mol% Y2O3 t+m ZrO2 + 4mol% Y2O3 t(m) ZrO2 + 6mol% Y2O3 c(t) ZrO2 + 8mol% Y2O3 c ZrO2(2Y) Continuous and isothermal t?m transformation Material: 1650?C sintered ZrO2-2mol% Y2O3 Cycle: a. heated with 100?C/min to 750?C and held for 5min; b. cooled with 100?C/min to various temperatures and held for 3h; c. finally cooled to room temperature with 100?C/min. Material: 1650?C sintered ZrO2-2mol% Y2O3 Cycle: a. heated with 100?C/min to 750?C and held for 5min; b. cooled with 100?C/min to various temperatures and held for 3h; c. finally cooled to room temperature with 100?C/min. Only isothermal part oft-m transformation Calculation of the activaton energy for isothermal t-m transformation in ZrO2-2mol% Y2O3 n = 0.7 Tsubakino et al (J. Mat. Sci., 26 (1991), 5521-5526) Q = 9.9 kCal/mol = 40kJ/mol 纯ZrO2陶瓷试样室温XRD图 X-ray diffraction result of specimen heated to 700?C Profiles of X-ray diffraction of specimen held at 350?C ZrO2(2Y) Profiles of X-ray diffraction of specimen held at various temperatures 300?C 250?C 200?C t-m等温转变激活能无压烧结 2Y(1600) Qm = 18.67 kJ/mol (1.47mm) 2Y(1400)