高孔隙率TiAl金属间化合物的制备及其阻尼响应特征的微观机制

A novel preparation process consisting of four stages (mixing, compacting, dissolution and sintering) will be developed to fabricate TiAl intermetallic compound porous material based on the combination effect of making pores arising from chemical reaction and physical space occupying. The maximum porosity up to 90% and pore size ranging from nanometer or micron to millimeter in order can be expected. The quantitative or semi-quantitative relation equation will be determined between preparation parameters, material chemical composition and pore structure parameters on the basis of the results of structure characterization and property testing. Combined with the analytical method of microscopic structure, the basic principles of internal friction and its analytical and testing methods are used to investigate the damping dependency relationship and correlated micro physical mechanism between material structure parameters, microscopic structure, thermodynamic treatment history, Nb content, measuring environment and damping response characteristics. The results will elucidate the contribution of all kinds of macro and micro defectse as well as the total response rule to the damping for the porous material due to their coupling and superimposing. Besides,basing on the analysis of typical internal friction phenomenon, the movement, distribution and interaction rule of the micro defects in TiAl intermetallic compound porous material can be disclosed,and furthermore, the dynamical process on the evolution of defect configurations can also be established. The results of the research will provide theoretical and experimental evidence for the application, the design on property and composition of the TiAl intermetallic compound porous material.

基于化学反应造孔和物理占位造孔的联合作用，发展一种新型的（均混+压制+脱溶+烧结）四阶段制备工艺，以获得孔隙率达90%、孔径在微纳米-毫米量级可控的TiAl金属间化合物多孔材料。在材料结构表征和性能测试基础上，确立制备工艺参数、材料化学组份和孔结构参数之间定量或半定量的关系方程。采用内耗的基本原理和分析测试方法，结合显微分析手段，研究TiAl金属间化合物多孔材料结构参数、微细观组织结构、热力学处理、Nb含量、测试环境与阻尼响应特征之间的依赖关系及其微观物理机制，阐明各种宏（微）观缺陷对阻尼的贡献及其耦合叠加对材料整体的阻尼响应规律；此外，通过对典型内耗现象的分析，揭示材料内部微观缺陷的运动、分布及交互作用规律，建立起缺陷组态发展演变的动力学过程。研究结果将为TiAl金属间化合物多孔材料的应用，性能和成分的设计提供理论和实验依据。

TiAl金属间化合物多孔材料拥有明确的性能优势和目标需求。本项目基于化学反应造孔和物理占位造孔的联合作用，发展了一种“均混-压制-脱溶-烧结”的制备工艺路线，实现了双孔结构TiAl多孔材料的制备，材料具有通孔结构，孔洞分布均匀，且孔隙率、孔径、孔型、孔结构可控，最高孔隙率可达90%。在材料结构表征和性能测试基础上，确立了制备工艺参数、材料化学组份和孔结构参数之间定量或半定量的关系方程。此外，工艺又可实现多样化孔隙结构和单孔结构TiAl多孔材料的制备。准静态压缩力学性能测试表明，TiAl多孔材料属于典型的脆性多孔材料，力学强度和相对密度的关系满足Gibson-Ashby方程，可通过正六面体单胞模型来理解。采用多功能内耗仪对TiAl多孔材料进行了系统的阻尼性能测试，结果表明，室温至600 oC，材料阻尼具有高度的热稳定性，与温度、应变振幅之间无明显依赖关系，但随测量频率的增加而增大。这源于TiAl金属间化合物原子间结合健既具有金属键特征，又具有共价键特征。TiAl多孔材料阻尼能力随孔隙率的增大或孔径的减小而增加，这种效应可通过内耗测试时应力集中和模式转换引起的膨胀能和畸变能的增加来理解。超过600 oC，材料高温背景内耗和位错等微观缺陷可动性增强，阻尼能力随温度快速增加。不同于TiAl多孔材料，致密TiAl合金超过600 oC出现一个与热激活弛豫过程有关的内耗峰，该峰随测量频率的增大，向高温方向移动，且随铝含量的增多，峰高和激活能均下降。分析认为，该峰起源于晶界弛豫，与晶界的粘滞性滑移有关，峰高和激活能的变化与晶粒的大小有关。研究结果将为TiAl多孔材料的应用、性能和成分的设计提供理论和实验依据。在本基金的资助下已发表SCI论文6篇和CSCD论文1篇（标注资助号）。