| Compared with titanium alloys,titanium matrix composites(TMCs)have higher specific strength and high temperature resistance,providing an ideal material for lightweight manufacturing of high-temperature automotive parts.At present,subsequent heat treatment is often used to adjust the microstructure and properties in the manufacturing process of TMCs,but the heat treatment time is long and the energy consumption is high.Electroshocking treatment(EST),as a high-efficiency and lowcost treatment method,is expected to provide a new way to improve the comprehensive properties of TMCs.In this paper,the particle-reinforced Ti B/Ti-2Al-6Sn were taken as the research object,the refinement effect of EST on Ti B reinforcement was studied,and the mechanism of the influence of Ti B refinement on the mechanical properties was discussed.In this paper,investigation on the variation of resistivity,microstructure evolution and mechanical properties of Ti B/Ti-2Al-6Sn before and after EST are carried out in detail.The important conclusions are shown as follows:(1)With the increase of EST time,the resistance of Ti B/Ti-2Al-6Sn first increased and then decreased,which was mainly due to the formation of defects at the reinforcement/matrix interface during the EST process.Scanning electron microscopy(SEM)was used to characterize and analyze the microstructure.It was found that after EST,Ti B was deflected and fractured under thermal stress and matrix extrusion,and was broken into small particles of about 50-312 nm.Its orientation were changed and homogenized significantly,and crack defects appear at the reinforcement/matrix interface,which affects its resistivity.(2)For the case of crack defects at the reinforcement/matrix interface,applying an external load during the EST process can achieve Ti B refinement while enhancing the integrity of reinforcement/matrix interface.The study found that when an external load of 0.3MPa was applied to the sample during EST,the Ti B was not only refined but also showed good contact with the matrix interface,and the cracks at the reinforcement/matrix interface were repaired.This is mainly due to the combined effect of thermal effect and non-thermal effect of EST and the external load.(3)Electron backscatter diffraction(EBSD)results show that EST can change the texture strength of grains.After EST for 0.06 s,the maximum relative texture strength of Ti B decreased from 13.09 to 12.97,and the maximum relative texture strength of αphase decreased from 3.11 to 1.58.The maximum relative texture strength of Ti B decreased from 12.97 to 8.10,and the maximum texture strength of α increased from1.58 to 1.99 after EST with an external load of 0.3 MPa simultaneously.The texture variation is mainly due to the change of grain orientation after Ti B refinement,and the redistribution of matrix grain orientation under the combined action of EST and the external load.The interface has also changed.(4)Comparing the mechanical properties of the materials before and after EST,it was found that the hardness of Ti B/Ti-2Al-6Sn decreased from 337.19 HV to 330.59 HV after EST,and the change was not obvious.In addition,after EST,the plasticity of Ti B/Ti-2Al-6Sn was enhanced,the yield strength decreased from 1009 MPa to 901 MPa,but the fracture strain increased from 24.18% to 25.37%.The reason is that the external load promotes the refinement of Ti B,enabling the reinforcement/matrix interface defects to be repaired.In conclusion,the synergistic effect of EST and external load can rapidly adjust the size of Ti B reinforcement from micron to nanometer level,and realize the refinement of short fiber Ti B reinforcement.At the same time,the matrix grain size and orientation are adjusted,and the texture strength is reduced after EST.It provides a new idea for the coordinated deformation of TMCs,which is of great significance for optimizing the mechanical properties of TMCs. |
PDF Full Text Request