Study On In-situ Synthesis Of Al₃Ti Intermetallic Compound Reinforced Aluminum Matrix Composite By Induction Heating

Due to their low density,thermal expansion coefficient,high strength,specific stiffness and specific modulus,good dimensional stability,thermal conductivity,and excellent wear resistance,Al-Ti intermetallic compounds are widely used in composite reinforcement.In this study,different Al₃Ti/Al composites were fabricated by in-situ synthesis method from aluminum and titanium fibers.The preforms prepared by mechanical and hot-extrusion methods were heated by induction heating,and the prepared composites were subjected to hot-extrusion.Through analyzing the microstructure,particles distribution,reaction mechanism and wear resistance of composite materials in different states,the effects of induction heating power and time,and hot-extrusion temperature and pressure on the properties of composites were explored.Under different induction heating power and time conditions,the degree of reaction between titanium fiber and liquid aluminum gradually increased,and a large number of Al₃Ti particles were distributed on the aluminum matrix.The size distribution of Al₃Ti particles was between 5-20μm.There were reaction zone and diffusion zone with different thickness around the unreacted titanium fiber.There were obvious microcracks on the surface of Al₃Ti particles located in the reaction zone and diffusion zone,which can accelerate the flaking and spreading of Al₃Ti particles.By comparing the microstructure of the composites prepared by induction heating and the traditional resistance furnace heating method,the Al₃Ti particles prepared by the induction heating method had longer diffusion distance and higher degree of dispersion.The kinetic exponents under different conditions are 0.786 and 0.33 respectively,which revealed that the induction heating makes the Al atoms have a higher diffusion rate,thereby improving the in-situ reaction rate,significantly.After hot-extrusion treatment,the pores on the matrix of the composite were significantly reduced,and the morphology and distribution of the particles change significantly with the change of the hot-extrusion conditions.With the increase of the hot-extrusion temperature,Al₃Ti particles change from spherical or nearly spherical to elongated shape,and the average value of particles size gradually increased from 10.93 μm at 560℃ to 17.27μm at 600℃.With the increase of hot-extrusion pressure,the particles gradually appear agglomeration and agglomeration from the dispersed state.At the same time,the particle size of Al₃Ti particles gradually decreases,and the average particle size of the particles decreased to 11.48μm at 30MPa.The friction and wear performance of the composites were tested by two-body wear experiments.By comparing and analyzing the wear rate and wear morphology,the wear resistance of the composite material under different conditions was explored.Under the conditions of induction heating,compared to the wear rate of pure aluminum of 14.43mg·cm^-2·h^-1,the wear rate of the composite was as low as 4.33mg·cm^-2·h^-1.After hot-extrusion treatment,the wear rate of the composite was significantly reduced,but under different hot-extrusion conditions,the trend of the wear rate was different.With the increase of the hot-extrusion temperature,the wear rate value shows a trend of first decreasing and then increasing,the lowest wear rate is 3.65mg·cm^-2·h^-1;with the increase of the hot-extrusion pressure,the wear rate had the lowest at 20MPa and the value was 3.35mg·cm^-2·h^-1.The wear morphology shows that the number and depth of grooves on the Al₃Ti particles were significantly reduced,which revealed that hot-extrusion treatment can significantly increase the density of the composite,and make the Al₃Ti particles better bond with the matrix.