Study On B₄C Reinforced Al/TC4 Laminated Composites

With the advancement of technology,the demand for light high-strength materials is increasing.In recent years,the Al/Ti laminate composite materials inspired by the shell lamellar structure have been brought out.Al/Ti laminated composites have great application potential in the fields of aerospace and armor protection because of their advantages of low density,high strength,simple preparation and low production cost.However,due to the room temperature brittleness of intermetallic compound Al₃Ti,the toughness of Al/Ti laminated composites is still far behind the practical application requirements.In this paper,Al/Ti laminated composites reinforced by B₄C sheet(B₄C_s)and B₄C particles(B₄C_p)were prepared by vacuum hot pressing method.The microstructure and composition of the two composites were observed and determined.The phase composition of diffusion layer in the two composites was analyzed.The effects of thickness ratio and vacuum hot pressing process on the impact toughness,bending strength and other mechanical properties of the two materials were studied.The mechanical properties of the two kinds of B₄C enhanced laminated composites and their respective matrices were compared.Besides,the strengthening effect of B₄C was determined,and their strengthening mechanism was analyzed.The main results obtained include:(1)In B₄C reinforced Al/Ti laminated composites,the diffusion layers are formed at Al-Ti and Al-B₄C interface,which contain Al₃Ti,Al B₂ and Al₄BC,respectively.With the increase of hot pressing temperature and time,the thickness of the Al-Ti diffusion layer is significantly improved.When Al is compeletely reacted into an intermetallic compound,the composite interface and the Al₃T center line position produce a large amount of defects,and the mechanical properties decrease greatly.(2)For B₄C_S reinforced Al/Ti laminated composite:As the number of B₄C layers increases,the impact toughness of the B₄C_S enhanced Al/Ti laminate composites increases,while the bending strength decreases.The impact toughness and bending strength of thes composites are increased by 51%and 38%respectively compared with that of the matrix by directly loading and absorbing energy and forming hardness gradient induced crack deflection in the composite.(3)For B₄C_P reinforced Al/Ti laminated composite:the sanmples with(0.5 mm TC4+0.2 mm Al),hot press temperature 710?,the liquid phase reaction time of Al 30 min have the best comprehensive mechanical properties,its impact toughness is 89 J/cm²,the bending strength is 1868 MPa,and the tensile strength is 952 MPa.The material prolongs the crack spread path by introducing B₄C particles,and extends the crack spread path.Moreover,a variety of strengthening stresses are generated at the interface between B₄C particles and Al,which makes the plastic toughness of the material significantly improved,51%,24%and 28%higher than that of the matrix,respectively.