Effects Of Ultrasonic And Pulsed Magnetic Field On Solidified Structure And Mechanical Properties Of SiC_P/AZ91D Composite Material

Magnesium matrix composites reinforced with SiC particles are widely used in 3C, automotive and aerospace fields, owing to their special physical and mechanical properties,such as light weight, high specific strength and stiffness, excellent wear resistance, damping performance and castability. Since the SiC particles are reunited in the matrix easily, which decreases its mechanical properties and limites the using scope. Effects of pulsed magnetic field, ultrasonic and compound treatment of ultrasonic and pulsed magnetic field on solidified structures and mechanical properties of SiCP/AZ91 D composites were investigated.The results show that during the preparation of SiCP/AZ91 D composites by pulsed magnet field, with the increase of voltage in the range of 0~250V, the primary grain is refined firstly and then coarsened, SiC particles disperse uniformly at first and then reunite in matrix. When the voltage reaches 200 V, the grain size is the smallest and distribution of SiC particles is the most uniform. With the increase of pulse frequency in the range of 0~5Hz, the grain is refined gradually and SiC particles distribute uniformly in matrix. With the increase of the mould temperature in range of room temperature to 600℃,grains coarsen gradually and SiC particles disperse uniformly. With the increase of pouring temperature in the range of 620℃~710℃, grains are coarsened and SiC particles reunite gradually. The best optimum parameters through orthogonal experiment are as follows: the pouring of temperature is 650℃, the mould temperature is 600℃ and the voltage is 250 V. With the increase of magnetic voltage and pulse frequency, the elongation of the composite increased obviously, but the tensile strength changs irregularly.During the preparation of SiCP/AZ91 D composites by ultrasonic, with the increase of output power in range of 0~900W, the primary grain is refined and SiC particles disperse uniformly in matrix. With the increase of treating time in the range of 0~120s, the primary grain is refined at first and then coarsened, the SiC particles disperse uniformly at first and then reunite in matrix. When the treating time reaches 60 s, SiC particles disperse uniformly in matrix. When the ultrasonic time reaches 90 s, grain size is the smallest. With the increase of the mould temperature or the pouring temperature, grain is coarsened and SiC particles reunite gradually in matrix. With the increase of output power, the mechanical properties of composites increase at first and then decrease. When the output power reaches 700 W, the mechanical properties of composites is the maximum. Compared with the sample without treatment, the tensile strength and elongation are improved by up to 80.5% and 101.9%, respectively. With the increase of treating time, the mechanical properties of composites increase at first and then decrease. When the treating time reaches 30 s, the mechanical properties of composite materials are the maximum.With compound treatment, the mechanical properties and solidified microstructure of composites are the best, compared with the sample without treatment. The tensile strength and elongation are improved by up to 213.7% and 137.0%, respectively. With the increase of the pouring temperature or the mould temperature, the primary grain coarsens gradually. When the pouring temperature is 620℃ or mould temperature is room temperature, the primary grain size is the smallest. When the pouring temperature is 670℃ or the mould temperature is 600℃, the SiC particles disperse uniformly in matrix. The change of the pouring temperature or the mold preheating temperature has no obvious effect on the mechanical properties of the composites.