SPS Preparation And Cutting Performance Study Of CNTs Reinforced TiAl Allo

TiAl alloy has good prospects for low density,high strength,and good thermal and electrical conductivity for low-pressure turbine blade applications;however,its poor room-temperature plasticity,brittleness,and processability severely limit its preparation and application in practice.Therefore,studying the room temperature mechanical properties and machined surface integrity of TiAl alloys is a reference value for the application and processing of TiAl alloy in practice.In this paper,CNTs and pre-alloyed powder Ti-48Al-2Cr-8Nb were selected to prepare CNTs/TiAl-based alloy composites by spark plasma sintering technique（SPS）,and the effects of CNTs content and sintering temperature on the microstructure and room temperature mechanical properties of the composites were investigated.The analysis shows that CNTs will react with the matrix to form granular Ti C and Ti₂Al C reinforced phases,and the granular Ti₂Al C phases stack at the grain boundaries to form stripes,which limit the grain growth.The content of Ti₂Al C phase will increase with the increase of CNTs content and sintering temperature.When the content of Ti C and Ti₂Al C phases is high,agglomeration will occur,resulting in defects such as pits and cracks in the composites,and the room temperature mechanical properties will be reduced.When the content of CNTs is 0.4%and the sintering temperature is 1000°C,the average grain size of the composites is about 32μm under the effect of fine crystal strengthening and second phase strengthening.The best mechanical properties of the composites at room temperature,the Vickers hardness and room temperature flexural strength are 377 HV and 879 MPa,respectively,and the room temperature compressive strength and maximum strain are 2554 MPa and 31.86%,respectively,and the fracture mode is dominated by grain-piercing fracture.The following results were obtained from the milling process experiments.The cutting force increases overall due to the generation of Ti C and Ti₂Al C phases,the cutting force will increase and then decrease with the increase of cutting speed,it will increase with the increase of feed and back draft,and the machined surface quality has the same trend with the cutting force.A set of suitable cutting parameters for the finishing of CNTs/TiAl-based alloy composites were determined:v_c=60 or 120 m/min,f_z=0.005 mm/z and a_p=0.05 mm.The machining surface defects generated by the milling process are grain pullout and edge popping.The main forms of wear of milling cutters are bonded wear and oxidation wear.