The Study On Powerder Processing Technology And Properties Of SiC_p/6061Al Composites With Medium Volume Fraction

Because of the advantages of light weight,high strength,high thermal conductivity and low thermal expansion,the medium volume fraction of SiC_p/Al composites are often used as the optical instruments material and the bent rod and brake materials of automobile.The SiC_p/Al composites prepared by traditional process often have many problems,such as poor interfacial wettability,low interfacial bonding strength,and the difficult to realize industrial production.Be based on these problems,the paper not only studied the surface modification of SiC particles and determined the best surface treatment process of SiC particles,but also prepared the SiC_p/Al composites with medium volume fraction by direct thermal sintering.Besides,the paper observed the microstructure and fracture morphology of the composites and observed and tested the mechanical properties and thermal properties of the composites by some testing techniques and methods.The main research contents of this paper include: When SiC particles were oxidized at high temperature,the effects of oxidation treatment on the morphology and surface composition of SiC particles and the influences of oxidation temperature and oxidation time on the thickness of oxide layer that formed on the surface of Si C particles were studied;The experiment analyzed the morphology and surface properties of SiC particles which were treated with K2ZrF6 salt solution and determined the two kinds of surface treatments of SiC particles;The SiC_p/6061 Al composites with Si C volume fraction of 35%-50% were prepared by direct thermal sintering method and the main technical parameters of the preparation process were determined;The experiment also studied the effects which the volume fraction of Si C and different pretreatment processes on the microstructure of composites and which the volume fraction of SiC and different pretreatment processes on density,fracture mechanism,mechanical and thermal properties of the composites.The results show that the technological parameters of the direct thermal sintering process incude the holding time,the continous pressure time and the sintering temperature.In the preparation process,the holding time is 15 min and the continuous pressure time is 4 min,and the sintering temperature is 680 ?.The composites prepared by the direct thermal sintering method exist defects such as the holes.The fracture mode of composites contain the ductile fracture of matrix,the interfacial debonding and cracking and the cleavage fracture of reinforced particles.With the increase of the volume fraction of SiC particles,the hardness of composites increased and the flexural strength decreased,while the thermal expansion coefficient and thermal conductivity of composites show a decreasing trend.When prepared the volume fraction of 40% SiC_p/6061 Al composites with the original SiC particles,the hardness is HB106,flexural strength is 311 MPa,thermal expansion coefficient less than7×10-6·K-1and thermal conductivity is 121 W·m-1·K-1.It was found that the mechanical properties and thermal physical properties of the composites were improved,when the original Si C particles were washed 3 h by 10%HF and then oxidized 10 h at 1100 ?,and washed by the saturated NaOH solution and then soaked 2 h by K2ZrF6 salt solution.After acid washing and oxidation treatment at high temperature,The hardness of the composites is HB115,the flexural strength is 325 MPa,the thermal expansion coefficient is 6.4×10-6·K-1 and the thermal conductivity is 132 W·m-1·K-1;After alkali washing and K2ZrF6 salt solution treatment,the hardness of the composites is HB125,the flexural strength is 350 MPa,the thermal expansion coefficient is 5.7×10-6·K-1 and the thermal conductivity is 145 W·m-1·K-1.