Fabrication And Properties Of Ti₃Si_1.2-xAl_xC₂ Solid Solution Materials

In this thesis, based on understanding of recent development and research on ternary layered compound MAX materials such as Ti₃SiC₂ etc, the preparation of Ti₃Si_1.2-xAl_xC₂(x=0.6) solid solution powder and Ti₃Si_1.2-xAl_xC₂(x=0.4,0.6) solid solution bulk materials by high-temperature pressureless calcining and in-situ hot-pressing sintering respectively have been particularly studied. Density, resistivity and flexural strength of Ti₃Si_1.2-xAl_xC₂(x=0.4,0.6) solid solution bulk materials have also been tested and analyzed. Preliminary studied the high-temperature oxidation behavior of Ti₃Si_1.2-xAl_xC₂(x=0.4) solid solution bulk materials, and obtained some result as below:The result indicates that the purity of Ti₃Si_1.2-xAl_xC₂(x=0.6) solid solution powder was greatly affected by the starting materials. Richer silicon and less carbon were propitious to the purity of solid solution, and Tin as an additive to the raw material obviously restrained the impurity of TiC. The calcining temperature and holding time also played an important role in the final products. The Ti₃Si_0.6Al_0.6C_1.98 solid solution powder was synthesized at 1450℃for 30 minutes using 3Ti/0.6Si/0.6Al/1.98C as starting material, which purity was 98.35 vol%, and The Ti₃Si_0.5Al_0.6Sn_0.1C_1.98 solid solution powder was synthesized at 1450℃for 60 minutes using 3Ti/0.5Si/0.6Al/Sn0.1/1.98C as starting material, which puritty was 98.63 vol%.Applying in-situ hot-pressing, when x was 0.4, high purity Ti₃Si_0.8Al_0.4C_1.95 bulk materials with its content over 98vol% were fabricated at 1600℃for 30 minutes under 30MPa using 3Ti/0.8Si/0.4Al/1.95C as starting material. When x was 0.6, high purity Ti₃Si_0.6Al_0.6C_1.98 bulk with its content over 98vol% was fabricated at 1450℃for 60 minutes under 30MPa using 3Ti/0.6 Si/0.6Al/1.98C as raw material. Through SEM and TEM observation and analyse, microstructure of Ti₃Si_1.2-xAl_xC₂ solid solution material was typical plate-like shape and layered structure.The results of physical property showed that the increase of Al lead to the decrease of density and flexural strength of the solid solution material,but increased electrical resistivity. The research of oxidation resistance results indicated that the oxidation behavior of Ti₃Si_1.2-xAl_xC₂(x=0.4)was more complex compared with Ti₃SiC₂ and Ti₃AlC₂.The oxidation weight gain curve of Ti₃Si_0.8Al_0.4C_1.95 didn't obey the parabolic law. At the earlier stage of the oxidation process, the oxidation weight gain curve of Ti₃Si_1.2-xAl_xC₂ (x=0.4) obey a linear law, and at the later stage the oxidation rate of Ti₃Si_1.2xAl_xC2 (x=0.4) slowed down。The compact Al₂O₃ oxidation layer formed on Ti₃Si_1.2-xAl_xC₂ (x=0.4) solid solution bulk materials during the oxidation process, which increased the oxidation resistance.