Strong And Ductile (ZrB₂+B₄C)/Al Composite Prepared By Ultrasound Magnetic Field Controlled Method And Its Structure And Mechanical Property

Particle reinforced aluminum matrix composites(PRAMCs)have broad application prospects in aerospace,transportation,weaponry and other fields due to their high specific strength,high specific modulus,high thermal conductivity,low expansion,heat resistance,and wear resistance.Among them,B₄C/Al composite materials are ideal light-weight structural materials and neutron-absorbing materials due to their low density,high strength,high neutron absorption capacity,and high thermal conductivity.However,like other particle-reinforced metal matrix composite materials,the thermal expansion coefficient mismatch and elastic modulus mismatch between the ceramic reinforcement and the matrix inevitably divide the matrix into the dislocation strengthening zone near the interface and the dislocation strengthening zone at the far interface.The unstrengthened area makes it difficult for the matrix micro-zones to deform cooperatively during the force deformation process,which results in strain localization and greatly reduces the plastic toughness.In addition,the poor wettability of the ceramic reinforcement,the oxide film on the Al melt surface hinders the introduction of the reinforcement,and the ceramic reinforcement easily reacts with Al to form harmful phases,restricting the low-cost"melt stirring method"to prepare B₄C/Al composites.Promote applications.In view of the above-mentioned scientific and technological problems,this research proposes to introduce nano-ZrB₂ particles into the unstrengthened micro-zones in the composite matrix by means of in-situ autogenous method to realize the synergistic deformation of the dislocation-strengthened zone near the interface and the nano-particle-strengthened zone at the far interface.The idea is to use the acoustic magnetic field to control the"melt stirring method".In the process of introducing B₄C reinforcement into the Al melt,K₂Zr F₆ is added to destroy the oxide film on the surface of the Al melt and realize the effective combination of the B₄C reinforcement and the Al melt.And make the Zr element in the melt excessive,react with the B₄C reinforcement to form an interface layer with good wettability,promote the uniform dispersion of the B₄C reinforcement and inhibit its reaction with the Al melt to form harmful phases,to prepare high strength and toughness(ZrB₂+B₄C)/Al composite material.The research of B₄C-Al composite interface shows that:Benefiting from the addition of K₂Zr F₆ during the process of introducing the B₄C reinforcement to destroy the surface oxide film of the melt and the introduction of Zr elements,the surface of the prepared B₄C/Al composite reinforcement is wrapped by a continuous and dense interface layer rich in Zr.The phase composition and microstructure analysis show that the interface layer is composed of ZrB₂ and Zr C,and the thickness is about 200-350nm.The interface layer with good wettability effectively improves the wettability of the B₄C reinforcement,and prevents the further reaction of B₄C and Al melt,so that the combination of B₄C and Al matrix in the prepared composite material is tighter and greatly improved the mechanical properties of composite materials.The analysis of the structure and performance of(ZrB₂+B₄C)/Al composite material shows that:The(ZrB₂+B₄C)/Al composite material prepared by the"melt stirring method"controlled by the acoustic magnetic field has advantages over the structure and performance of the composite material prepared by the traditional mechanical stirring method.The electromagnetic/ultrasonic field can promote the in-situ nano-ZrB₂ particles the synthesis,inhibit the formation of Al₃Zr,improve the uniform distribution of ZrB₂ and B₄C particles,and improve the mechanical properties of composite materials.Among them,with the increase of the content of nano-ZrB₂particles,the tensile strength of the composite material increases,but the elongation first increases and then decreases.When the content of ZrB₂ particles reaches 0.5vol.%,the composite material has the best comprehensive performance and tensile strength.The strength and elongation are 161 MPa and 13.8%,respectively.The main reason why the elongation of the composite material increases first and then decreases is that the high specific surface energy of the nano-ZrB₂ particles tends to agglomerate.When the content of the nano-ZrB₂ particles reaches 0.5vol.%,the particles agglomerate significantly,which leads to increased stress concentration and reduces the material's performance.(ZrB₂+B₄C)/AA6016 composite material hot-extruded microstructure and performance research shows that:After the(ZrB₂+B₄C)/AA6016 composite material undergoes hot extrusion,the distribution of the reinforcement particles changes significantly.The extrusion deformation causes the clusters of nano-ZrB₂ particles to be broken,from the original flocs to the fibrous distribution along the extrusion direction.After T6 heat treatment,the matrix presents an obvious dynamic recrystallized structure,in which the recrystallized grains preferentially nucleate and grow near the ZrB₂particles.With the increase of the content of ZrB₂ particles,the recrystallized grains distributed near the ZrB₂particles become finer,and the{111}texture is also increasing.Extrusion significantly improves the mechanical properties of composite materials.Among them,(1vol.%ZrB₂+10vol.%B₄C)/AA6016 composite material has the best comprehensive mechanical properties,with a tensile strength of391Mpa and an elongation rate of 11.8%.