Severely deformed aluminum sheets were processed by friction stir processing(FSP) with Si C nanoparticles under different conditions to improve the mechanical properties of both the stir zone and the heat affected zon...Severely deformed aluminum sheets were processed by friction stir processing(FSP) with Si C nanoparticles under different conditions to improve the mechanical properties of both the stir zone and the heat affected zone(HAZ).In the case of using a simple probe and the same rotational direction(RD) of the FSP tool between passes,at least three FSP passes were required to obtain the appropriate distribution of nanoparticles.However,after three FSP passes,fracture occurred outward from the stir zone during transverse tensile tests;thus,the strength of the specimen was significantly lower than that of the severely deformed base material because of the softening phenomenon in the HAZ.To improve the mechanical properties of the HAZ,we investigated the possibility of achieving an appropriate distribution of nanoparticles using fewer FSP passes.The results indicated that using the threaded probe and changing the RD of the FSP tool between the passes effectively shattered the clusters of nanoparticles and led to an acceptable distribution of Si C nanoparticles after two FSP passes.In these cases,fracture occurred at the HAZ with higher strength compared to the specimen processed using three FSP passes with the same RD between the passes and with the simple probe.The fracture behaviors of the processed specimens are discussed in detail.展开更多
（38vo1% SiCp ＋ 2vo1% A1203f）/2024 A1 composites were fabricated by pressure infiltration. Graphite powder was introduced as a forming filler in preform preparation, and the effects of the powder size on the microst...（38vo1% SiCp ＋ 2vo1% A1203f）/2024 A1 composites were fabricated by pressure infiltration. Graphite powder was introduced as a forming filler in preform preparation, and the effects of the powder size on the microstructures and mechanical properties of the final com- posites were investigated. The results showed that the composite with 15 μm graphite powder as a forming filler had the maximum tensile strength of 506 MPa, maximum yield strength of 489 MPa, and maximum elongation of 1.2%, which decreased to 490 MPa, 430 MPa, and 0.4%, respectively, on increasing the graphite powder size from 15 to 60 μm. The composite with 60 μm graphite powder showed the highest elastic modulus, and the value decreased from 129 to 113 GPa on decreasing the graphite powder size from 60 to 15 μm. The differences between these properties are related to the different microstructures of the corresponding composites, which determine their failure modes.展开更多
文摘Severely deformed aluminum sheets were processed by friction stir processing(FSP) with Si C nanoparticles under different conditions to improve the mechanical properties of both the stir zone and the heat affected zone(HAZ).In the case of using a simple probe and the same rotational direction(RD) of the FSP tool between passes,at least three FSP passes were required to obtain the appropriate distribution of nanoparticles.However,after three FSP passes,fracture occurred outward from the stir zone during transverse tensile tests;thus,the strength of the specimen was significantly lower than that of the severely deformed base material because of the softening phenomenon in the HAZ.To improve the mechanical properties of the HAZ,we investigated the possibility of achieving an appropriate distribution of nanoparticles using fewer FSP passes.The results indicated that using the threaded probe and changing the RD of the FSP tool between the passes effectively shattered the clusters of nanoparticles and led to an acceptable distribution of Si C nanoparticles after two FSP passes.In these cases,fracture occurred at the HAZ with higher strength compared to the specimen processed using three FSP passes with the same RD between the passes and with the simple probe.The fracture behaviors of the processed specimens are discussed in detail.
基金funded by the National Natural Science Foundation of China (Grant No. 51174029 and No. 51374028)National High Technology Research and Development Program of China (No. 2013AA031005)Beijing Higher Education Young Elite Teacher Project (No. YETP0417)
文摘（38vo1% SiCp ＋ 2vo1% A1203f）/2024 A1 composites were fabricated by pressure infiltration. Graphite powder was introduced as a forming filler in preform preparation, and the effects of the powder size on the microstructures and mechanical properties of the final com- posites were investigated. The results showed that the composite with 15 μm graphite powder as a forming filler had the maximum tensile strength of 506 MPa, maximum yield strength of 489 MPa, and maximum elongation of 1.2%, which decreased to 490 MPa, 430 MPa, and 0.4%, respectively, on increasing the graphite powder size from 15 to 60 μm. The composite with 60 μm graphite powder showed the highest elastic modulus, and the value decreased from 129 to 113 GPa on decreasing the graphite powder size from 60 to 15 μm. The differences between these properties are related to the different microstructures of the corresponding composites, which determine their failure modes.
