Preparation And Properties Of TiB₂/Al Based Composites Prepared By Freeze Casting-pressure Infiltration

TiB₂ceramic reinforced Al composites(TiB₂/Al)have high specific stiffness,high specific strength,good wear resistance and have good application prospects in the military,aerospace,and transportation fields.However,it is difficult to solve the matching problem of high strength and toughness of composite materials by using traditional preparation methods such as powder metallurgy and in-situ generation methods.In this paper,based on the idea of biomimetic shell nacre layered structure,A380 aluminum alloy and Al-Cu alloy are selected as the matrix of the composite material,and TiB₂ceramic is used as the reinforcing phase.TiB₂/A380 and TiB₂/Al-Cu layered composites with imitation shell nacre were successfully prepared by freezing casting and pressure infiltration process.By adjusting the preparation process parameters of the freezing casting,the microstructure of the composite material is controlled,and the composite material with different lamella spacing and microscopic morphology is prepared.The microstructure,mechanical properties and fracture mechanism of TiB₂/Al-based composites are also studied.The main results of this paper are as follows:(1)The TiB₂/A380 layered composite material was prepared by freezing casting and pressure infiltration technology.In the composite material,the ceramic layer and the metal layer are arranged alternately in a belt shape,and the interface between the ceramic and the metal is well combined.The test results of the mechanical properties of the composite material show that the performance of the TiB₂/A380 layered composite material shows obvious anisotropy.TiB₂/A380 layered composite material shows excellent fracture toughness.However,the presence of Si particles at the TiB₂/?-Al interface of the composite material reduces the bonding strength of the interface,which is not conducive to the enhancement of the toughness of the composite material.(2)The TiB₂/Al-Cu layered composite material was prepared by freezing casting and pressure infiltration technology,and the influence of different heat treatment processes on the composite material was studied.After the mechanical performance test,it is found that the strength and toughness of the sample after the heat treatment process and solution treatment is better than that of the as-cast sample.This is mainly due to the existence of the coarse Al₂Cu phase in the as-cast sample matrix easily becomes the source of cracks,resulting in the entire test Kind of break.(3)TiB₂/Al-Cu layered composites with different initial solid content of ceramics were prepared by freezing casting and pressure infiltration technology,revealing that as the initial solid content of ceramics increases,the thickness of the composite ceramic layer increases,and the strength of the composite Improved but reduced resilience.(4)TiB₂/Al-Cu layered composites with different gelatin content were prepared by freezing casting and pressure infiltration technology.The study found that as the content of gelatin increases,the microscopic morphology of the composite material changes from a lamellar shape to a‘honeycomb'grid shape.The strength and fracture toughness of composite materials has been improved.This was mainly due to the grid structure effectively suppressing the plastic deformation of the metal layer and causing multiple cracks.