Study On Preparation Process And Properties Of Particle Reinforced Aluminum Matrix Composites

As one of the most widely used metal materials,aluminum and aluminum alloys play an irreplaceable role in the fields of aerospace,automobiles,building materials,etc.However,with the development of industries,traditional aluminum alloys have gradually failed to meet the demand for material properties.Aluminum matrix composites not only have light weight,good electrical and thermal conductivity,but also excellent corrosion resistance and damping performance.They can also be designed to meet the needs of different applications.In this paper,in situ sintering of Al-TiO₂-B₂O₃ system and in-situ melt reaction of Al-TiO₂-B₂O₃ system and Al-KBF₄-K₂TiF₆ system were used to prepare the composites,reaction mechanism and properties of particle reinforced aluminum matrix composites was studied,the following conclusions are drawn:?1?In the in-situ sintering method,the powder was subjected to ball milling for12 hours.The sintered compact obtained at 850°C and holding for 30 minutes was dense and almost free of pores.The Al₂O₃ particles were fine and evenly distributed in the matrix,and the size was about 1?m;a small amount of TiAl₃ particles exist in the form of short rods,the length is also about 1?m;TiB₂ particles are associated around Al₂O₃ particles,with dimensions at the nanoscale;Al B₂ particles are larger,sizes from 4 to 8?m.The reaction processes of different systems are carried out step by step.Free elements[Ti]or[B]are generated firstly.After the active elements have diffused and reacted,the required reinforced particles can be generated;This step-by-step process is governed by the reaction kinetics.The higher the concentration of free activated atoms,the higher the temperature,the easier it is to break the kinetic energy barrier.The Al-TiO₂-B₂O₃ ternary reactant system,due to the formation of the TiB₂ phase,starts at a lower temperature and proceeds most thoroughly.?2?In the in-situ melt reaction of Al-TiO₂-B₂O₃ system,the in-situ reaction could not be promoted by changing the reaction sequence and pressing pressure of the prefabricated blocks.The in-situ melt reaction can take place with the aluminum foil wrapped composite powder at 850°C and can improve the wettability of the reinforcing particles with the aluminum matrix so that a small amount of reinforcing particles can enter the matrix,but the wettability improvement is not obvious.When the doping amount of aluminum powder is 3/5,the in-situ reaction proceeds most violently.When the doping amount of aluminum powder is 2/1,the in-situ reaction proceeds mildly.?3?Ultrasonic vibration can maximize the tensile strength and wear resistance of the material during the preparation of particle reinforced A356 matrix composites by in-situ melt reaction process of Al-KBF₄-K₂TiF₆ system.The tensile strength reaches172 MPa increased by 20.3%compared with the A356 alloy;the friction coefficient and wear amount were the lowest,and the wear resistance was the best.The strength of A356 alloy increases gradually with TiB₂ particle content.When the particle content reaches 12%,the tensile strength reaches a maximum of 186 MPa,which is30%higher than that of A356 alloy.When the reinforcement phase is TiB₂+Al₃Ti,with the increase of the total content of TiB₂+Al₃Ti,the strength of the composite material increases first,then decreases and then increases.When the TiB₂+Al₃Ti content is 2%,the material strength reaches a maximum of 173 MPa.Compared with TiB₂ and TiB₂+Al₃Ti,the performance of TiB₂ reinforcement is better than that of TiB₂+Al₃Ti.The material is in the form of quasi-cleavage brittle fracture.The wear patterns of the composites shift from oxidation wear and adhesive wear to abrasive wear and oxidation wear with the increase of the content of particles in the matrix.