Basic Research On Al-B₄C Composites Prepared By High-efficiency Stirring Casting

Particle-reinforced aluminum matrix composites are capable of blending the advantages of metallic aluminum and reinforcing phase particles.It has the advantages of light weight,good ductility,excellent toughness of aluminium,and the advantages of high hardness and good abrasion resistance of the reinforcing phase particles.Therefore,the research and application of particle reinforced aluminum matrix composites are the most widely used.In view of the mechanical stirring casting method of impeller type and particle dispersion relation is less studied,and poor uniformity of particle defects,high volume fraction to add,the research group proposed a highly efficient stirring method to prepare Al-B4C composites.This method achieves the uniform addition of particles by optimizing the stirring paddles and strengthening the mixing conditions.Physical simulation parts:the high-efficiency stirring paddle type was determined through the water model experiment,and the stirring paddle type stirring process parameters were analyzed.The results show:the standard deviation for the use of a six-bladed open turbine is 0.048384,while the standard deviation for a six-bladed open turbine is 0.13002,the six-bladed open-type turbine blades have better suspension and dispersion effects on particles than the six-bladed open-type turbine blades;when using a six-bladed open-type turbine paddle,the increase of the stirring speed is beneficial to the suspension and dispersion of the particles;the reduction of the immersion depth is conducive to the dispersion of the particles;the increase ratio of impeller diameter to inner diameter of stirred tank is beneficial to the suspension and dispersion of the particles;particle size reduction facilitates particle suspension and dispersion.The thermal experiments parts:investigated the effect of the addition of B4C particles on the Al-B4C composite material under electromagnetic stirring conditions.The results show that at 900?,B4C particles were uniformly dispersed in Al-B4C composites by directly adding 5%volume fraction of B4C particles.The content of B4C complexed with Al matrix is only 50.27%of the amount of B4C added,and the amount of B4C complexed with Al is less.In the pretreatment of Al-B2O3-C composite powder with high energy ball milling,the average particle size of the composite powder at the milling speed of 300rpm was 4.706 ?m,and the average particle size of the composite powder was 14.873 ?m after the milling time increased to 90 min,the ball-milled Al-B2O3-C composite powder was coated on Al foil and added into the Al melt at 900?,and the Al-B4C-Al2O3 composite could be formed by in-situ reaction.After that,Al-B4C composites were prepared using different stirring methods and different mechanical stirring speeds.The results showed that:at 900?,compared with the AlB4C composites prepared by electromagnetic stirring,when the volume fraction of 5%B4C was added,the content of B4C compounded with Al-based Al-B4C composite material increased from 50.27%to 70.54%of the amount of B4C added.,and the content of B4C complexed with Al increased,and the uniformity of dispersion of B4C particles is enhanced.With the mechanical stirring speed increased from 200rpm to 400rpm,the content of B4C complexed with Al increased,and the uniformity of dispersion of B4C particles is enhanced.