Study On The Effect Of Ce On The Hot Tearing Susceptibility And Elevated Temperature Mechanical Properties Of 5TiB₂/ZL205A Composite

The particle-reinforced aluminum matrix composites combine the advantages of particle-reinforced phase high modulus,wear resistance,corrosion resistance,and thermal stability,so that it has better comprehensive mechanical properties.It is the most typical particle-reinforced aluminum matrix composites for the TiB₂particle-reinforced Al-Cu matrix composites prepared by the in-situ autogenous method,in which TiB₂particles is the main reinforcement.Because of its simple preparation method,it not only does not require large-scale changes to the existing equipment,but also realizes that the particle size of the TiB₂ reinforcement phase reaches the nanometer level in the composite,so that the composite has excellent mechanical properties and is widely used in aerospace,automotive Industry and other fields.However,due to the wide solidification temperature range of Al-Cu alloy,hot tearing defects are easily generated during the solidification process,which affects the yield and performance of TiB₂ particle-reinforced aluminum matrix composite products.Therefore,it is of great practical value to study an economical,simple and effective method to improve the hot tearing susceptibility of TiB₂ particle reinforced aluminum matrix composites.In this paper,the most representative high-strength Al-Cu alloy-ZL205A is used as the matrix material of the composites.Then,5TiB₂/ZL205A composite containing 5%mass fraction TiB₂ particles as the reinforcing phase was prepared by in-situ autogenous melt technology.The hot tearing susceptibility of 5TiB₂/ZL205A composite was improved by adding the rare earth element Ce.Through XRD phase analysis,EDS energy spectrum scanning element analysis and TEM diffraction spot crystal structure analysis,it is concluded that there is a new phase of?1-Al₈Cu₄Ce in the composites.The study found that with the continuous increase of Ce content,the grain size,solidification temperature range,and hot tearing susceptibility value of5TiB₂/ZL205A composite all show a downward trend.Through comprehensive analysis,the mechanism of Ce on the improvement of grain size,solidification temperature range and hot tearing susceptibility is obtained.In addition,through the analysis of the composites structure,hot cracks,and hot tearing fracture,it is concluded that the addition of Ce gradually disperses the TiB₂ particle agglomerates in the composite,and gradually refines the associated Al₃Ti phase,thereby making the structure more uniform.And with the increase of Ce content in the composite,the grain boundary bridging gradually increases at the end of solidification,thereby preventing the initiation and propagation of hot cracks,and finally achieving the purpose of improving the hot tearing susceptibility of composites.It is necessary to study the effect of rare earth Ce on the mechanical properties of5TiB₂/ZL205A composite at room temperature and high temperature because of the formation of?₁-Al₈Cu₄Ce heat-resistant stable phase during the solidification of the composites with the addition of Ce.The results of the study found that adding 1%Ce to the 5TiB₂/ZL205A composite has the best room temperature and high temperature tensile properties.At room temperature,the tensile strength of the composite can reach 243 MPa,and the elongation rate can reach 13%,and at 300?,the tensile strength can reach 215 MPa,and the elongation rate can reach 11.8%,which shows that the Ce-containing composites has excellent high-temperature mechanical properties.Through the analysis of the structure,fracture,?'precipitates and?₁precipitates of the composites,it is concluded that Ce can significantly improve the tensile properties of 5TiB₂/ZL205A composite at room temperature and high temperature.In order to further improve the room temperature and high temperature mechanical properties of 1Ce-5TiB₂/ZL205A composite,hot rolling process is used to improve the room temperature and high temperature mechanical properties of1Ce-5TiB₂/ZL205A composite.It was found that the bulk phase in the composite was crushed after 40%compression deformation under 400?,and the TiB₂ particles bonded with the aluminum matrix more firmly and the microstructure became more uniform.After rolling at a reduction ratio of 40%,the T6 state 1Ce-5TiB₂/ZL205A composite has excellent mechanical properties at room temperature or high temperature.The tensile strength of the composite can reach 323MPa at room temperature,and the elongation rate can reach 12%.And at 300?,the tensile strength of the composite can reach 310 MPa,and the elongation rate can reach 11%.It can be found that the mechanical properties of the 1Ce-5TiB₂/ZL205A composite have little change at room temperature and high temperature,indicating that the composite has good heat resistance.The results show that the room temperature and high temperature mechanical properties of 5TiB₂/ZL205A composite can be improved by adding 1%Ce to 5TiB₂/ZL205A composite combined with appropriate hot rolling process.