Microstructure And Mechanical Properties Of TiAl Alloy By Solidification Conditions And Addition Of CNTs

TiAl based alloy is one of the widely used alloys in traditional industry and manufacturing industry.It has the characteristics of light density,excellent high temperature performance,high specific stiffness and high specific strength.However,with the rapid development of modern science and technology,the traditional process of TiAl alloy can not meet the needs of modern industrial development.In particular,the room temperature plasticity of TiAl alloy limits its service at high temperature for a long time.In order to improve the plasticity of TiAl alloy,the effects of solidification conditions on the alloy were studied by high-pressure solidification and rapid solidification,and the effects of the addition of carbon nanotubes(CNTs)on the microstructure and mechanical properties of the alloy were explored.Meanwhile,the microstructure evolut ion and strengthening mechanism of the alloy were also analyzed.The evolution of phase structure of TiAl alloy after high pressure solidification was studied.The relationship between dislocation density,microstructure refinement and properties were revealed.The results showed that the high-pressure solidification can increase the dislocation density in the alloy and strengthen the nano-hardness.However,the superheating condition can lead to the dislocation density decrease,which weakens the mechanical properties of the alloy.The effect of roll speed on microstructure and mechanical properties of TiAl alloy under rapid solidification were studied.The results show that the primary phase changes to?phase and the lattice constant of?phase increases when the roll speed is 16 m/s,the content of?phase decreases and the?₂ phase increases,the nanohardness of the ribbons also increases.When the wheel speed is 24 m/s,the nano hardness of the ribbons is 5.82 GPa.The effect of CNT contents on microstructure evolution and fracture mode of TiAl alloy was also studied.The experimental results show that the content of Ti₂Al C in the alloy is proportional to the content of CNT.The compressive strength and compression ratio of TiAl alloy increased first and then decreased.The optimum compressive strength and compression ratio of the alloy were 1904.25 MPa and 9.84%,respectively,when 1.0 wt.%CNTs was added.The controlling mechanism of mechanical properties of TiAl alloy is the combination of fine grain strengthening and?phase weakening.The results show that rapid solidification and high-pressure solidification are effective methods to strengthen the TiAl alloy,and the addition of CNTs can further enhance the mechanical properties of TiAl alloy.