新型Ti_3AlC_2-Al_2O_3/TiAl_3复合材料的组织结构与性能

利用Al-TiO2-TiC体系,通过机械球磨和反应热压制备出Ti3AlC2与Al2O3两相原位内生成增强TiAl3金属基复合材料。借助DSC、XRD、SEM和TEM研究了复合材料的反应机制、显微组织、力学性能及抗氧化性能。结果表明,球磨50h后的复合粉末经1 250℃/50 MPa保温10min烧结后可得到组织均匀细小且致密的Ti3AlC2-Al2O3/TiAl3复合材料,其密度、维氏硬度、室温三点弯曲强度、断裂韧性及压缩强度分别为3.8g/cm3、8.4GPa、658.9 MPa、7.9 MPa·m1/2和1 742.0 MPa,1 000℃的高温压缩强度为604.1 MPa。Ti3AlC2-Al2O3/TiAl3复合材料的增韧机制主要包括Ti3AlC2和Al2O3颗粒的剥离、Ti3AlC2相导致的裂纹偏转和桥接以及Ti3AlC2颗粒的变形及层裂。Ti3AlC2-Al2O3/TiAl3复合材料在700~1 000℃温度区间内生成的氧化层虽不致密,但仍表现出优异的抗高温循环氧化性能。

Microstructure and properties of new type Ti3AlC2-Al2O3/TiAl3 composites

The TiAl₃ matrix intermetallic composites reinforced by in-situ synthesized two phases of Ti₃AlC₂ and Al₂O₃ were produced by mechanically ball-milled and hot pressing of Al-TiO₂-TiC system. The reaction mechanism, microstructure, mechanical properties and oxidation-resistance properties of the composites were investigated using DSC, XRD, SEM and TEM. The results indicate that dense Ti₃AlC₂-Al₂O₃/TiAl₃ composites with homogeneous and pyknotic microstructure can be obtained by sintering 50 h ball-milled power mixture at 1 250 ℃/50 MPa for 10 min. The density, Vickers hardness, three-point bending strength, fracture toughness and compressive strength at room temperature of Ti₃AlC₂-Al₂O₃/TiAl₃ composites reach 3.8 g/cm³, 8.4 GPa, 658.9 MPa, 7.9 MPa·m^1/2 and 1 742.0 MPa, respectively, and the elevated-temperature compressive strength at 1 000 ℃ reaches 604.1 MPa. The toughening mechanism of Ti₃AlC₂-Al₂O₃/TiAl₃ composites is primarily attributed to the pull-out of Ti₃AlC₂ and Al₂O₃ particles, crack deflection and crack bridging by Ti₃AlC₂ phase, and the deformation and delamination of Ti₃AlC₂ particles. Tough the oxidation scales generated in the temperature range from 700 to 1 000 ℃ are not dense, the Ti₃AlC₂-Al₂O₃/TiAl₃ composites still exhibit excellent cyclic oxidation resistance.