内生增强铝基复合材料微波热爆反应机制与组织演变

In situ aluminum matrix composites has been attracted because that the in situ reinforcements are of no pollution, high thermal stability, good compatibility and high interface strength with the matrix. Thermal explosion reaction method is one of the effective fabrication methods. However, its high energy consumption, long preparation period, easy coarsening in microstructure and heavy burden on environment. Combining the microwave technology with the thermal explosion synthesis for fabricating aluminum matrix composites is a novel technology, which will result in the significant decrease in ignition temperature, great increase in reaction velocity, refining and improving the distribution of the reinforcements, substantial decrease in energy consumption and good in concordance with the environment. In this project, Al-ZrO2-B2O3 reaction system as our research object, the Gibb's free energy,entropy and enthalpy thermodynamic parameters are studied to indicate the thermodynamic mechanism of this system. To indicate the microwave thermal explosion reaction kinetics, the reaction rate and activation energy, numerical simulation and microwave non-thermal effects of the microwave thermal explosion reaction are researched. We change the molar ratio of the components and analyze the composition, morphology, microstructure and distribution of reinforcements to reveal the mechanism of microstructure evolution. Based on above investigations, a new fabrication technology with high energy efficiency and friendly environment relationship, and in situ reinforced aluminum matrix composites with excellent properties can be obtained. Microwave thermal explosion theory of the reinforced aluminum composites can also be initially established.

内生增强铝基复合材料因其增强体无污染，热力学稳定，与基体的相容性好、界面结合强度高而备受关注。热爆反应法为其有效制备方法之一被广泛采用。然而，该法能耗高、制备周期长、组织易粗化、环境负担重。为此，申请者将微波技术引入热爆反应法合成内生增强铝基复合材料，此时，发现起爆温度明显降低，反应速率显著提高，增强体细化、分布改善，能耗降低、环境友好。本项目以Al-ZrO2-B2O3体系为研究对象，研究吉布氏自由能、熵和焓等热力学参数，揭示微波热爆反应的热力学机制；研究微波作用下的反应活化能、反应速率，以相同初末温度比较法探讨微波非热效应，数值模拟微波热爆反应过程，揭示微波热爆反应动力学机制；改变组分摩尔比，分析微波作用下反应组织的组成、形貌、微观结构及其分布规律，揭示组织演变机制。通过本项目研究可获得节能、高效、环境友好的新型反应制备技术和性能优异的内生增强铝基复合材料，初步形成微波热爆反应理论。

内生增强金属基复合材料因其增强体无污染，热力学稳定，与基体的相容性好、界面结合强度高而备受关注。热爆反应法为其有效制备方法之一被广泛采用。然而，该法能耗高、制备周期长、组织易粗化、环境负担重。本课题以Al-Cu-Ti-C和Al-Cu-Ti-B两种体系，分别采用微波热爆和传统热爆制备了TiC和TiB2增强Al-Cu合金基复合材料；以Ti-Al-B、Ti-Al-C体系微波热爆法制备了TiB2和TiC颗粒增强TiAl基复合材料。此时，发现起爆温度明显降低，反应活化能显著减小，反应速率显著提高，增强体细化、分布改善，能耗降低、环境友好。主要结论如下：.1.Al-Cu-Ti-C和Al-Cu-Ti-B系微波加热和传统加热均对应一个热效应峰。Al先和Ti反应生成中间产物TiAl3，随后C原子和B原子将TiAl3中的Al置换出来形成TiC和TiB2。微波加热时两体系的反应活化能分别为41.4kJ/mol和33.8kJ/mol；传统加热时则分别为270.0kJ/mol和113.8kJ/mol。.2.传统加热时，TiB2/TiAl的反应分两阶段：1）Al和B生成少量AlB2；Ti和Al生成TiAl3放热剧烈；AlB2在高温下分解，与Ti分别生成TiAl3和TiB2。2）TiAl3逐渐转变为Ti3Al和TiAl两相。对应的反应活化能分别为723.80kJ/mol和310.05kJ/mol。TiC/TiAl系的反应同样分两阶段：1）Ti和Al生成TiAl3；2）TiAl3转变为Ti3Al和TiAl及增强相TiC的生成。对应的反应活化能分别为435.61kJ/mol和466.30kJ/mol。微波热爆时两步反应合并进行，TiB2/TiAl(5vol.%, 2h)和TiC/TiAl(5vol.%, 2h)的反应活化能分别降为43.21kJ/mol和26.97kJ/mol。.3.传统加热时，Al-Cu-Ti-C、Al-Cu-Ti-B体系的增强体易于偏聚，微波加热时，增强体颗粒尺寸细小、分布相对均匀，反应更加充分。微波热爆合成10vol%TiC/Al-Cu、10vol%TiB2/Al-Cu热压后抗拉强度分别为367.0MPa和329.1MPa，较传统加热分别提高14.6%和30.1%。