原位合成Al_2O_3颗粒增强双相TiAl基复合材料的组织与性能

Microstructure and mechanical properties of in situ Al_2O_3 particles reinforced two-phase TiAl-based composites

以Ti-Al-TiO2反应体系为基础,添加不同含量的Nb2O5粉,采用压力协助原位合成Al2O3颗粒增强的双相TiAl基复合材料,对复合材料的组织和力学性能进行了分析讨论,并探讨了其增韧机制。结果表明:Nb2O5的掺杂使复合材料的相对密度和硬度得到提高,抗弯强度和断裂韧性在Nb2O5掺杂量为6%(质量分数)时达到最大,分别为398.38 MPa和6.992 MPa.m1/2。微观组织分析表明,获得了双相组织,Al2O3颗粒分布于基体晶界处;随Nb2O5的掺杂量增大,Al2O3颗粒呈细小弥散分布,同时基体晶粒尺寸也减小。双相基体晶粒的细化及Al2O3颗粒的弥散分布是赋予材料高韧性的主要增韧机制。

In situ Al2O3 particles reinforced two-phase TiAl-based composites were prepared by pressure-assisted high-temperature reaction sintering of Ti-Al-TiO2-Nb2O5 system. The microstructure and mechanical properties of the composites were investigated. The toughening mechanism was also analysed. The results show that the relative density and Rockwell hardness of the composites increase with increasing Nb2O5 content. When the Nb2O5 content is 6% （mass fraction）, there presents a better bending strength and fracture toughness, and the bending strength attains 398.38 MPa, moreover, the fracture toughness reaches 6.992 MPa·m^1/2. The analysis of the microstructures reveals that it obtains a submicron α2/γ, dual phase structure, and the Al2O3 particles distribute on the grain boundary. The in situ Al2O3 particles are dispersively distributed and the grains are refined with increasing Nb2O5 content. Two-phase TiAl grain refining and Al2O3 particles dispersive distribution are the main toughening mechanisms .