Fabrication And Mechanical Properties Of Insitu TiCp+TiB₂p/ZL205A Aluminum Matrix Composites

In-situ particle reinforced aluminum matrix composites have the advantages of small particle size,good bonding effect between particles and matrix,clean interface,simple process and good machinability.They have been widely used in automobile,aerospace and other fields.The in-situ TiCp+TiB₂p/ZL205A aluminum matrix composites were prepared by using Al-Ti-B₄C system instead of Al-Ti-B system,which not only reduces the cost,but also realizes the micro-nano phase synergistic enhancement of aluminum matrix composites.At present,there are few studies on TiCp+TiB₂p/ZL205A dual-phase particle reinforced aluminum matrix composites,and the dispersion of in-situ particles is still one of the problems to be overcome.In this paper,micro-nano synergistic reinforced TiCp+TiB₂p/ZL205A composites were prepared by contact reaction method.The effect of powder molar ratio on the microstructure of the composites was studied.In order to solve the problem of uneven particle dispersion,rare earth element Ce was introduced,and the effects of rare earth content and ultrasonic stirring on mechanical properties were studied.The main research contents and results are as follows:The effects of different powder molar ratios on the microstructure of the composites were studied.The results show that when the molar ratio of Ti:B₄C:Al=2.5:1:6,the reaction is relatively complete,and Al₃Ti is almost invisible in the microstructure.There are a small amount of TiB₂ particles agglomerated and casting defects in the microstructure of the as-cast composite.When Ti:B₄C:Al=3:1:6,there is a large size agglomeration.When Ti:B₄C:Al=3.5:1:6,Al₃Ti becomes longer.Therefore,the ratio of Ti:B₄C:Al=2.5:1:6 is adopted,which also lays a foundation for the subsequent preparation process.The effects of rare earth Ce content on the microstructure and mechanical properties of the composites were studied.The results show that the addition of Ce element improves the dispersion of reinforced particles in the matrix of TiCp+TiB₂p/ZL205A composites,inhibits the agglomeration of particles in the composites,and refines the grain size.When the rare earth content is 0.1%,the particle dispersion uniformity is good,and the grain size refinement is the most obvious.According to the theory of fine grain strengthening,grain refinement is also beneficial to the improvement of the comprehensive properties of TiCp+TiB₂p/ZL205A composites.The tensile strength and elongation of TiCp+TiB₂p/ZL205A composites are 426.3 MPa and 1.56%,respectively.Compared with the matrix,the tensile strength is slightly improved,but the elongation is greatly reduced.On the basis of adding rare earth,the composite melt was further ultrasonically stirred,and the effects of ultrasonic parameters（time and power）on the microstructure and mechanical properties of the composites were studied.The results show that when the ultrasonic time is 3 min and the ultrasonic power is 2400 W,the nano-TiB₂ particles generated by the reaction are evenly distributed and the microstructure is network.However,after ultrasonic stirring,Ti C particles play a core role in the nucleation of Al₂Cu.In addition,ultrasonic stirring will not inhibit the formation of Al₃Ti,resulting in the coarsening of Al₃Ti,so that the mechanical properties of TiCp+TiB₂p/ZL205A composites cannot be increased,and the tensile strength is 368.0 MPa.The above research provides a basis for improving the agglomeration of composite particles.