原位自生Al2O3柱晶增韧低膨胀莫来石陶瓷直接增材制造

Basing on the urgent demand on high temperature oxide structural material in the field of high thrust weight ratio aero-engine and efficient gas turbine, and aiming at realizing the structural-functional manufacturing of high performance ceramic parts, this project mainly studies on the stress and cracking problems during direct additive manufacturing of ceramics by means of laser engineered net shaping. Low expansion mullite is synthesized by in-situ reaction of alumina and silicon oxide in order to reduce the thermal stress of shaping process. The toughness of mullite matrix is further improved by adding in situ autogenic Al2O3 columnar crystal with excess Al2O3 to inhibit the cracking behavior in the process of ceramic fabrication. Through the crack propagation analysis of fabricated Al2O3 parts, the toughening mechanism of in-situ autogenic Al2O3 columnar crystal is revealed and its toughness increment model is established. With the application background of hot components of the aero engine and gas turbine, the high temperature stability and the high temperature mechanical properties of the forming structure are evaluated and analyzed. The purpose of this project is to propose a low stress additive manufacturing technology for high toughness oxide ceramics, and reveal the toughening mechanism of in-situ toughening phase in ceramic solidification structure, so as to provide theoretical support for the final realization of structural-functional integrated manufacturing of high performance ceramic parts.

本项目以高推重比航空发动机及高效率燃气轮机对高温抗氧化结构材料的迫切需求为背景，以实现高性能陶瓷构件的结构-功能一体化制造为技术目标，针对陶瓷构件直接增材制造过程中应力大易开裂等技术挑战，基于激光近净成形技术及多相材料熔体析出有序性特征，利用Al2O3与SiO2原位反应合成低膨胀莫来石陶瓷以降低成形过程热应力，通过添加过量Al2O3原位自生Al2O3柱晶进一步提高莫来石基体韧性，实现陶瓷成形过程中开裂行为的有效抑制；通过不同比例过量Al2O3成形制件的裂纹扩展分析，揭示原位自生Al2O3柱晶的增韧机制并建立其韧性增量模型；针对航空发动机及燃气轮机热端部件的使役要求，分析评价成形结构的高温稳定性及高温力学性能。本项目旨在提出一种高韧性氧化物陶瓷的低应力增材制造技术，揭示原位自生增韧相在陶瓷凝固组织中的韧化机理，为最终实现高性能陶瓷零件的结构-功能一体化制造提供理论支撑及工艺指导。

陶瓷材料因具有卓越的热力学性能，在关键领域具有重要的应用价值。针对航空航天领域对轻质耐热高性能结构材料快速制造的迫切需求，本项目利用激光增材制造技术制造了氧化铝基熔体自生陶瓷，重点关注了降低热应力、抑制裂纹形成、微观结构和力学性能的理解。以先进陶瓷粉末为初始材料，研究了激光直接能量沉积成形熔体自生的莫来石、Al2O3//莫来石、Al2O3/ZrO2共晶/亚共晶/过共晶、功能梯度陶瓷等陶瓷材料的工艺可行性、参数优化、气孔裂纹缺陷、微观组织及性能特征等内容，分析了气孔裂纹形成机制，并给出了减少气孔和抑制裂纹的方法，研究了微观组织形成和演变机制，提出了熔体自生氧化铝基陶瓷材料性能显著提升的热处理方法，评价了材料高温稳定性、高温强度和抗热震性等热相关性能，实现了质轻高性能熔体自生氧化物陶瓷的快速激光增材制造，并为其在高温结构材料中的应用提供详实的理论和工艺指导。其中，所制备熔体自生陶瓷的室温抗弯强度可以达到504 MPa，断裂韧性可以达到3.54 MPa·m1/2，1000 ℃时的强度可以保持到247 MPa。本项目的开展实现了高性能陶瓷构件的结构-功能一体化制造的技术目标，推动了熔体自生陶瓷材料在更极端工况及更广泛领域的应用。