The mechanical and tribological properties of Cu-based powder metallurgy （P/M） friction composites containing 10wt%-50wt% oxide-dispersion-strengthened （ODS） Cu reinforced with nano-Al2O3 were investigated. Additi...The mechanical and tribological properties of Cu-based powder metallurgy （P/M） friction composites containing 10wt%-50wt% oxide-dispersion-strengthened （ODS） Cu reinforced with nano-Al2O3 were investigated. Additionally, the friction and wear behaviors as well as the wear mechanism of the Cu-based composites were characterized by scanning electron microscopy （SEM） in conjunction with energy-dispersive X-ray spectroscopy （EDS） elemental mapping. The results indicated that the Cu-based friction composite containing 30wt% ODS Cu exhibited the highest hardness and shear strength. The average and instantaneous friction coefficient curves of this sample, when operated in a high-speed train at a speed of 300 km/h, were similar to those of a commercial disc brake pad produced by Knorr-Bremse AG （Germany）. Additionally, the lowest linear wear loss of the obtained samples was （0.008 ± 0.001） mm per time per face, which is much lower than that of the Knorr-Bremse pad （（0.01 ± 0.001） mm）. The excellent performance of the developed pad is a consequence of the formation of a dense oxide composite layer and its close combination with the pad body.展开更多
Tungsten nanoparticle-strengthened Cu composites were prepared from nanopowder synthesized by a sol–gel method and in-situ hydrogen reduction.The tungsten particles in the Cu matrix were well-dispersed with an averag...Tungsten nanoparticle-strengthened Cu composites were prepared from nanopowder synthesized by a sol–gel method and in-situ hydrogen reduction.The tungsten particles in the Cu matrix were well-dispersed with an average size of approximately 100–200 nm.The addition of nanosized W particles remarkably improves the mechanical properties,while the electrical conductivity did not substantially decrease.The Cu–W composite with 6 wt%W has the most comprehensive properties with an ultimate strength of 310 MPa,yield strength of 238 MPa,hardness of HV 108 and electrical conductivity of 90%IACS.The enhanced mechanical property and only a small loss of electrical conductivity demonstrate the potential of this new strategy to prepare W nanoparticle-strengthened Cu composites.展开更多
P-containing 316L stainless steel was prepared by powder metallurgy technology using gas atomized alloy powder and phosphorus-iron alloy powder as raw materials.P addition was beneficial to sintering densification.Wit...P-containing 316L stainless steel was prepared by powder metallurgy technology using gas atomized alloy powder and phosphorus-iron alloy powder as raw materials.P addition was beneficial to sintering densification.With 0.6 wt.%P addition,the density increased from 7.60 to 7.82 g/cm^(3).In such case,the samples with 0.6 wt.%P addition should be sintered at a lower temperature of 1200℃.Otherwise,there were coarse grain boundary precipitates,which would seriously deteriorate the performance of stainless steel.In the case of suppressing the formation of coarse precipitates,appropriate P content had a beneficial effect on apparent morphology,hardness and strength of stainless steel.When 316L-0.6 wt.%P sample was sintered at 1200℃,the hardness and tensile strength were increased to 86.3 HRB and 672.8 MPa,respectively,and the elongation still reached 38.1%.Besides,it also had good corrosion resistance.展开更多
Microstructural evolution and mechanical properties of in situ TiB2/A1 composites fabricated with exothermic reaction process under high-intensity ultra- sound produced by the magnetostrictive transducer were investig...Microstructural evolution and mechanical properties of in situ TiB2/A1 composites fabricated with exothermic reaction process under high-intensity ultra- sound produced by the magnetostrictive transducer were investigated. In this method, the microstructure and grain refining performance of the TiB2/A1 composites were characterized by optical morphology （OM）, scanning electron microscopy （SEM）, energy-dispersive spec- trometer （EDS）, and X-ray diffraction （XRD） analysis. Microstructural observations show a decreasing trend in the grain size of the composites due to the ultrasound and the content of TiB2 particles in the composites. Compared with the process without ultrasound, the morphology and ag- glomeration of TiB2 particles are improved by high-in- tensity ultrasound. Meanwhile, it is proposed that the formation of TiBz particles occurs via the transformation from TiA13, and at the optimal amount of the reactants, the conversion efficiency of TiA13 into TiB2 almost reaches up to 100 %. Finally, the effects of high-intensity ultrasound and TiB2 particles on the mechanical properties of the TiB2/A1 composites were also discussed.展开更多
In this paper,the effects of P doping on magnetic properties and microstructure were studied in Nd-Fe-B sintered magnets.With P doping,the grain size gets refined and the distribution of the main phase is optimized du...In this paper,the effects of P doping on magnetic properties and microstructure were studied in Nd-Fe-B sintered magnets.With P doping,the grain size gets refined and the distribution of the main phase is optimized due to the reduction of the liquidus temperature.The liquidus temperature for the 0.05 wt% P-doped magnets is 1022 K,while that for the P-free magnets is 1038 K.As P content increases,the liquidus temperature significantly decreases.Clear and continuous grain boundary phases are formed in the P-containing magnets with smaller grain size.The optimized microstructure with average grain size of 8.43 μm is obtained in the 0.05 wt% P-doped magnets,which is approximately 0.69 μm smaller than that of P-free sintered magnets (9.12 μm).Though P is usually thought to be an impurity element,it might be beneficial in Nd-Fe-B sintered magnets with proper addition.The coercivity of the 0.05 wt% P-doped magnets could be increased to 1283 kA·m-1,with slight changes of the remanence and the maximum magnetic energy product.NdPO4 phases in the grain boundary are of hexagonal structure,while those at the triple junctions have monoclinic structure.Activated sintering is achieved by doping proper P element in the Nd-Fe-B sintered magnets.展开更多
基金financially supported by the National High Technology Research and Development Program of China (No. 2013AA031104)
文摘The mechanical and tribological properties of Cu-based powder metallurgy （P/M） friction composites containing 10wt%-50wt% oxide-dispersion-strengthened （ODS） Cu reinforced with nano-Al2O3 were investigated. Additionally, the friction and wear behaviors as well as the wear mechanism of the Cu-based composites were characterized by scanning electron microscopy （SEM） in conjunction with energy-dispersive X-ray spectroscopy （EDS） elemental mapping. The results indicated that the Cu-based friction composite containing 30wt% ODS Cu exhibited the highest hardness and shear strength. The average and instantaneous friction coefficient curves of this sample, when operated in a high-speed train at a speed of 300 km/h, were similar to those of a commercial disc brake pad produced by Knorr-Bremse AG （Germany）. Additionally, the lowest linear wear loss of the obtained samples was （0.008 ± 0.001） mm per time per face, which is much lower than that of the Knorr-Bremse pad （（0.01 ± 0.001） mm）. The excellent performance of the developed pad is a consequence of the formation of a dense oxide composite layer and its close combination with the pad body.
基金supported by the Fundamental Research Funds for the Central Universities (No. FRF-TP-18-029A2)State Key Lab of Advanced Metals and Materials of China (No. 2019-Z10)
文摘Tungsten nanoparticle-strengthened Cu composites were prepared from nanopowder synthesized by a sol–gel method and in-situ hydrogen reduction.The tungsten particles in the Cu matrix were well-dispersed with an average size of approximately 100–200 nm.The addition of nanosized W particles remarkably improves the mechanical properties,while the electrical conductivity did not substantially decrease.The Cu–W composite with 6 wt%W has the most comprehensive properties with an ultimate strength of 310 MPa,yield strength of 238 MPa,hardness of HV 108 and electrical conductivity of 90%IACS.The enhanced mechanical property and only a small loss of electrical conductivity demonstrate the potential of this new strategy to prepare W nanoparticle-strengthened Cu composites.
基金This work was supported by the National Natural Science Foundation of China(Nos.U21A200305 and 51925401)the Research Project on Characteristic Innovation of University Teachers in Foshan City(No.2021XJZZ07)the Scientific and Technological Innovation Foundation of Foshan,USTB(No.BK21BE001).
文摘P-containing 316L stainless steel was prepared by powder metallurgy technology using gas atomized alloy powder and phosphorus-iron alloy powder as raw materials.P addition was beneficial to sintering densification.With 0.6 wt.%P addition,the density increased from 7.60 to 7.82 g/cm^(3).In such case,the samples with 0.6 wt.%P addition should be sintered at a lower temperature of 1200℃.Otherwise,there were coarse grain boundary precipitates,which would seriously deteriorate the performance of stainless steel.In the case of suppressing the formation of coarse precipitates,appropriate P content had a beneficial effect on apparent morphology,hardness and strength of stainless steel.When 316L-0.6 wt.%P sample was sintered at 1200℃,the hardness and tensile strength were increased to 86.3 HRB and 672.8 MPa,respectively,and the elongation still reached 38.1%.Besides,it also had good corrosion resistance.
基金financially supported by the National High Technology Research and Development Program of China(No.2013AA031104)
文摘Microstructural evolution and mechanical properties of in situ TiB2/A1 composites fabricated with exothermic reaction process under high-intensity ultra- sound produced by the magnetostrictive transducer were investigated. In this method, the microstructure and grain refining performance of the TiB2/A1 composites were characterized by optical morphology （OM）, scanning electron microscopy （SEM）, energy-dispersive spec- trometer （EDS）, and X-ray diffraction （XRD） analysis. Microstructural observations show a decreasing trend in the grain size of the composites due to the ultrasound and the content of TiB2 particles in the composites. Compared with the process without ultrasound, the morphology and ag- glomeration of TiB2 particles are improved by high-in- tensity ultrasound. Meanwhile, it is proposed that the formation of TiBz particles occurs via the transformation from TiA13, and at the optimal amount of the reactants, the conversion efficiency of TiA13 into TiB2 almost reaches up to 100 %. Finally, the effects of high-intensity ultrasound and TiB2 particles on the mechanical properties of the TiB2/A1 composites were also discussed.
基金financially supported by State Key Lab of Advanced Metals and Materials(No.2018-Z06)the Fundamental Research Funds for the Central Universities(No.FRFTP-18-025A1)
文摘In this paper,the effects of P doping on magnetic properties and microstructure were studied in Nd-Fe-B sintered magnets.With P doping,the grain size gets refined and the distribution of the main phase is optimized due to the reduction of the liquidus temperature.The liquidus temperature for the 0.05 wt% P-doped magnets is 1022 K,while that for the P-free magnets is 1038 K.As P content increases,the liquidus temperature significantly decreases.Clear and continuous grain boundary phases are formed in the P-containing magnets with smaller grain size.The optimized microstructure with average grain size of 8.43 μm is obtained in the 0.05 wt% P-doped magnets,which is approximately 0.69 μm smaller than that of P-free sintered magnets (9.12 μm).Though P is usually thought to be an impurity element,it might be beneficial in Nd-Fe-B sintered magnets with proper addition.The coercivity of the 0.05 wt% P-doped magnets could be increased to 1283 kA·m-1,with slight changes of the remanence and the maximum magnetic energy product.NdPO4 phases in the grain boundary are of hexagonal structure,while those at the triple junctions have monoclinic structure.Activated sintering is achieved by doping proper P element in the Nd-Fe-B sintered magnets.
