【作者】 安惠中；

【导师】 陈沙鸥； 隋万美；

【作者基本信息】 青岛大学 ， 材料学， 2004， 硕士

【摘要】 本论文利用热分析、X-射线衍射、扫描电镜、透射电镜和原子力显微镜等分析测试手段，对纳米m-ZrO₂／Al₂O₃复相系统的烧结行为、显微结构、马氏体相变以及力学性能进行了研究，观察了ZrO₂体积分数不同对复相体系烧结行为、基体约束应力、晶粒长大、ZrO₂相变的影响。 本论文实验工作观察了0.6μm Al₂O₃和60nmZrO₂颗粒制备的单相样品及不同ZrO₂初始含量的复相样品的烧结行为。样品的烧结曲线表明，与单相Al₂O₃样品相比，单相ZrO₂样品的最大致密化速率高，而中后期阶段的起始温度和最大致密化速率对应的温度都低，两者的最终线收缩率十分接近，表明纳米颗粒的烧结行为优于亚微米颗粒。在Al₂O₃／ZrO₂复相材料中，样品的烧结行为主要受体积分数占多数的相的控制，烧结曲线与所对应的单相样品相比移向高温区，中后期阶段的起始温度、最大致密化速率对应温度也相应移向高温，但最大致密化速率降低，表明异相粒子的加入对烧结起到阻碍作用。对2℃／min和5℃／min两种升温速率样品的烧结曲线的比较，发现烧结速率的不同对样品的烧结行为影响不大。 密度测试结果表明，Al₂O₃体积分数占多数的样品的致密度都比单相Al₂O₃的低，而ZrO₂体积分数占多数的样品的致密度都比单相Al₂O₃的高，与样品的烧结行为相一致。通过扫描电镜对样品粒径的观察发现烧结样品中Al₂O₃、ZrO₂的粒径长大与烧结行为的分析也是一致的，单相Al₂O₃的平均粒径是2.16μm，是Al₂O₃粉料的3.5倍；随着ZrO₂体积分数的增加，样品中Al₂O₃的粒径逐渐减小，在含有80vol．％ZrO₂样品中的平均粒径降低为0.78μm，是Al₂O₃粉料的1.3倍。同样，随着Al₂O₃体积分数的增加，样品中ZrO₂的粒径也逐渐减小，在含有80vol．％ZrO₂样品中的平均粒径为0.24μm，是ZrO₂粉料的4倍，而在含有20vol．％ZrO₂样品中的平均粒径为0.14μm，是ZrO₂粉料的2.3倍。 另一方面，通过差热分析观察了Al₂O₃体积分数对ZrO₂相变温度的影响。结果显示ZrO₂相变温度存在热滞现象，而且随着Al₂O₃体积分数的增加，上、下马氏体点都有降低，下降幅度分别在60℃范围和190℃范围，下马氏体点降幅明显大于上马氏体点，相变热滞温差增大，这是由于基体约束力的增加对ZrO₂相变结构重组所需越过的势垒的影响在升降温过程中不同的缘故。 通过力学性能的测试结果发现，样品的显微硬度随着ZrO₂含量的增加，逐渐降低，这是由于复合材料样品杨氏模量减小的缘故。而断裂强度和断裂韧性除了10vol．纳米:仆zro:/A1203复相系统的烧结行为、显微结构和相变的研究%zro:样品的强度和韧性较之单相AbO3有所提高外，其它样品都有降低，表明只有稳定的四方ZrO:的存在刁‘能对一样品有强韧化作用。更多还原

【Abstract】 The present thesis used thermal analyse, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) etc to study sintering behavior, microstructure, martensite phase transformation and mechanical properties of nanometer m-ZrO2 /Al2O3 composite system. Simultaneously, we have also observed the effect of the initial volume fraction changes of ZrO2 on sintering behavior, constraining stress of matrix, grain growing and ZrO2 phase transformation.The sintering behavior was studied for monophase Al2O3 and ZrO2 samples as well as composite samples with different initial volume fraction of ZrO2 using raw materials of 0.6 m Al2O3 powder and 60nm ZrO2 powder respectively in this thesis. The results of sintering curves indicated that the max densification rate of monophase ZrO2 sample was greater than the counterpart of monophase Al2O3, but the starting temperature of intermediate and last stages as well as the corresponding temperature of max densification rate were lower than the counterpart of monophase Al2O3. Moreover shrinkage ratios of both monophase samples were very closed. These results displayed that the sintering behaviors of nanometer powders was better than sub-micron powders. In m-ZrO2 /Al2O3 composite materials, the sintering behaviors of samples were mainly controlled by the phase whose volume fraction was in the majority. Comparing with the corresponding monophase samples, the sintering curves as well as the starting temperatures of intermediate and last stages and the corresponding temperature of max densification rate of composites moved to higher temperature range, but the max densification rate were lower. These conclusions demonstrated that the hetero-phase powder mixed in composites inhibited sintering of samples. Otherwise, comparing the sintering velocity of 2 C/min with that of 5 C/min, we found the difference of sintering velocity did not obviously affect sintering behavior.The result of density experiment manifested that the density of samples in which the volume fraction of A12O3 was in the majority was lower than that of monophase A12O3, while the volume fraction of ZrO2 was in the majority was higher than that of monophase Al2O3. This conclusion agreed well with the sintering behavior of samples. The grain growing of A12O3 and ZrO2 observed by SEM was corresponding to the analyses of sintering behavior. The mean grain size of monophase Al2O3 was 2.16 m, which was 3.5 times the size of Al2O3 powder. With the increasing of ZrO2 initial volume fraction, the grain size of Al2O3 in samples was decreasing. The mean grain size of A12O3 in the sample contained 80vol. %ZrO2 was 0.78um, which was 1.3 times the size of A12O3 powder. And with the increase of Al2O3 volume fraction, the grain size of ZrO2 in samples was decreasing. The mean grain size of ZrO2 in the sample contained 80vol. % ZrO2 was 0.24 m, which was 4 times the size of Zr02 powder; while the mean grain size of ZrO2 in the sample contained 20vol. %ZrO2 was 0.14um, which was 2.3 times the size of ZrO2 powder.On the other hand, the effect of AbOs volume fraction on ZrO2 phase transformation was observed by the differential thermal analysis (DTA). The result showed there was a thermal retardation in ZrO2 phase transformation temperature. With the increasing of AbOa volume fraction, both high and low martensite temperatures were decreasing in the rage of 60 C and 1 90 C respectively. The variation ranges of low martensite temperatures were obviously greater than that of high martensite temperatures. The difference was growing in temperature of thermal retardation due to phase transformation. The reason was different influences during temperature increasing and decreasing on the potential barriers due to structure reorganization needed to get over in ZrO2 phase transformation as the constraining stress of matrix increasing.The experimental results of mechanical properties manifested that the micro-hardness got down with the increasing of the initial volume fraction of ZrO2 because of y更多还原