Study On Preparation And Properties Of Wear Resisting Aluminum Matrix Composites

Al-20%Si and SiCp/Al-7%Si matrix composite were studied based on their potential application in automobile piston and cylinder sleeve.These two kinds of aluminum matrix composites were prepared respectively by Internal Cooling Modification process and Screw Pushing process.The influence of two different preparation processes on the microstructure and properties of above two kinds of aluminum matrix composites was investigated by OM,SEM,EDS,XRD and friction test,to improve possibility of the potential application in the field of piston and cylinder sleeve.The result of the Al-20%Si alloy treated by Internal Cooling Modification process was shown as followed in which the microstructure and property were checked under different preparation condition.(1)The average grain size and shape factor of primary Si were affected by stirring temperature,stirring speed and mass ratio internal cooling block to aluminum melt.According to the orthogonal test,the effect of mass ratio of internal cooling block to aluminum melt on the microstructure was much more greater than other technical factor and it was also the optimized process of Internal Cooling Modification process.When stirring temperature was 700?,stirring speed was 1800rpm,mass ratio of internal cooling block to aluminum melt was 15%,the optimized grain size of primary Si was 18?m and shape factor was 0.71.(2)With the decrease of grain size of primary Si,the Brinell hardness and Tensile strength of Al-20%Si sample increased.(3)With the decrease of grain size of primary Si,the average frictional coefficient of Al-20%Si decreased.On the contrary the wear rate showed the opposite trend as decrease of the grain size of the primary Si.The average frictional coefficient and wear rate of sample were 0.25 and 6.1857×10-14m3·N-1·m-1 respectively in the optimum process.Microstructure and properties of SiCp/Al-7%Si matrix composite prepared by Screw Pushing process was studied in different process parameters.Experimental results showed:(1)The larger the particle size of SiC was,the better the dispersion of SiC in the melt.The more SiC particles were added,the more serious for agglomeration.In the nearly confined spaces,the larger the stirring speed,the better the dispersion of SiC in the melt.The interface bonding was enhanced between SiC and matrix.(2)With the increase of adding volume of SiC and stirring speed,the Brinell hardness and Tensile strength of SiCp/Al-7%Si increased.While with the increase of SiC particle size,the Brinell hardness and Tensile strength of SiCp/Al-7%Si decreased.(3)With the increase of adding volume of SiC and SiC particle size,the average frictional coefficient of SiCp/Al-7%Si increased.The higher the stirring speed,the smaller the average frictional coefficient of SiCp/Al-7%Si.While the wear rate showed the opposite trend compared with the average frictional coefficient.(4)According to microstructure and friction and wear data,the optimized process was that SiC particles size was 10?m,volume of SiC addition was 5%and stirring speed was 1500rpm in which the average frictional coefficient and wear rate of sample were 0.22 and 6.3455×10-14m3·N-1·m-1 respectively in the optimum process.The wear behavior of Al-20%Si and SiCp/Al-7%Si presented abrasive wear and adhesive wear.The fiction and wear properties compared between Al-20%Si and SiCp/Al-7%Si in the optimum process,showed that the average frictional coefficient and friction coefficient stability of the SiCp/Al-7%Si was better than that of Al-20%Si.However the wear rate of SiCp/Al-7%Si was just slightly greater than Al-20%Si.In general,the friction and wear properties of SiCp/Al-7%Si matrix composite was better than Al-20%Si alloy in the aspect of reducing frictional resistance.