微纳米颗粒增强TiAl基复合材料组织与室温性能研究

Microstructure and mechanical properties of micro-nano particles reinforced TiAl composites at room temperature

摘要:

原位自生颗粒增强金属基复合材料是提高金属材料强韧性的有效途径,本文采用放电等离子烧结技术 (SPS),以氧化石墨烯、碳化硅、氮化硼为增强体,原位自生制备TiAl基复合材料,研究增强相体对TiAl基复合材料显微组织演变及室温性能的影响。结果表明,增强体的改变直接影响了TiAl基复合材料第二相形貌和分布。添加石墨烯后,在TiAl合金α2和γ片层界面处弥散析出微纳米尺度第二相Ti2AlC；添加碳化硅在基体中分别生成微米级晶界相Ti5Si3，微纳米片层间相Ti2AlC；添加氮化硼未能在TiAl合金α2和γ片层界面处析出微纳米第二相，而是纳米级TiB2和Ti2AlN相析出在晶界处与基体形成连续核壳结构；复合添加石墨烯和氮化硼既能在片层间原位析出Ti2AlC相,又能在晶界处形成核壳结构。TiAl基复合材料的室温压缩性能和摩擦磨损性能均得到有效提高,复合添加石墨烯和氮化硼可获得优异的室温性能。TiAl基复合材料的析出相调控为合金设计提供了新思路,进一步突破TiAl合金性能极限。

Abstract:

The mixed powders of Ti-48Al-2Nb-2Cr alloy with multilayer graphene oxide, SiC particles and BN nanosheets were sintered by spark plasma sintering (SPS) at 1300 ℃, and the different reinforcement on microstructure evolution and properties of TiAl composites were investigated. The results showed that the microstructure of composites was significantly changed with the addition of different reinforcement. The micro-nano Ti₂AlC in-situ precipitated at the interface of α₂ lath and γ lath of TiAl matrix after adding graphene. While a microstructure composed of networked core-shell (CS) structured cells can be formed in TiAl matrix with the addition of SiC particles and BN nanoplatelets. Moreover, Ti₂AlC can be in situ precipitated and CS structure can be formed by adding graphene and BN nanoplatelets simultaneously. The compressive properties and wear properties of TiAl composites were improved significantly, which showed optimal performance by adding graphene and BN nanoplatelets simultaneously. TiAl composites provided a new idea for alloy designation and broken through the performance limitation of TiAl alloy.