Study On The Microstructure And Properties Of Carbon Fiber-H62 Brass Matrix Composite Prepared By Friction Stir Processing

Carbon fiber(CF)reinforced H62 brass matrix composites were prepared by friction stir processing(FSP).The effects of CF content and welding speed on the microstructure and properties of CF-h62 brass matrix composites were studied by variable orthogonal experiment.The results show that the surface of the composites processed by friction stir processing is better without macro defects,porosity or holes.The microstructure of the joint was observed by optical microscope,scanning electron microscope(SEM)and transmission electron microscope(TEM).It is found that the microstructure is fine equiaxed crystal,which is the result of dynamic recrystallization.With the increase of welding speed from 20 mm/min to 60 mm/min,the average grain size of welded joint increases from 5 ?m is reduced to 2 ?m.When the depth of the hole filled with CF is 1.5mm and the welding speed is 40mm/min,the distribution of CF in the composite area is the most uniform.The hardness of the composites was significantly increased by the addition of CF.When the hole depth of CF is 1 mm and the welding speed is 20mm/min,the average hardness of the joint reaches 166.8 HV.With the increase of hole depth,the hardness of the composite decreases.The uniformity of CF distribution has an effect on the hardness of the composites,and the uniformity of CF distribution is beneficial to improve the hardness of the composites.The hardness of the composites decreases with the increase of welding speed.The addition of CF improves the wear resistance of the composites.CF has a disordered graphite structure.As a reinforcing phase,CF forms a solid lubricating film on the friction surface of the composite,which plays a role of lubrication and friction reduction,and improves the wear resistance of the composite.The uniformity of CF distribution has an effect on the wear resistance of the composite.When the depth of the hole filled with CF is 1.5 mm and the welding speed is 40 mm/min,the wear loss of the composite in the friction and wear test is the smallest,which is 0.0339 g.The wear surface of friction and wear test sample was analyzed by SEM.It is found that the main wear mechanism is the dynamic repair of self lubricating film formed by CF and abrasive wear,accompanied by adhesive wear.The more uniform the distribution of CF is,the more conductive it is.Although grain refinement is not conducive to the improvement of electrical conductivity,due to the combined effect of twinning and CF,the electrical conductivity of the composite increases from 15100 S/cm to 17800 S/cm.TEM observation showed that CF was well bonded to the substrate.Grains,grain boundaries,dislocations,deformation twins and annealing twins can be observed.