The mass of high-speed trains can be reduced using the brake disk prepared with SiC network ceramic frame reinforced 6061 aluminum alloy composite （SiCn/Al）. The thermal and stress analyses of SiCn/Al brake disk dur...The mass of high-speed trains can be reduced using the brake disk prepared with SiC network ceramic frame reinforced 6061 aluminum alloy composite （SiCn/Al）. The thermal and stress analyses of SiCn/Al brake disk during emergency braking at a speed of 300 km/h considering airflow cooling were investigated using finite element （FE） and computational fluid dynamics （CFD） methods. All three modes of heat transfer （conduction, convection and radiation） were analyzed along with the design features of the brake assembly and their interfaces. The results suggested that the higher convection coefficients achieved with airflow cooling will not only reduce the maximum temperature in the braking but also reduce the thermal gradients, since heat will be removed faster from hotter parts of the disk. Airflow cooling should be effective to reduce the risk of hot spot formation and disc thermal distortion. The highest temperature after emergency braking was 461 °C and 359 °C without and with considering airflow cooling, respectively. The equivalent stress could reach 269 MPa and 164 MPa without and with considering airflow cooling, respectively. However, the maximum surface stress may exceed the material yield strength during an emergency braking, which may cause a plastic damage accumulation in a brake disk without cooling. The simulation results are consistent with the experimental results well.展开更多
SiC p/6061Al alloy composite was welded by using TIG and pulsed-TIG welding (P-TIG) without addition of filler metal, or with addition of Al-Si or Al-Mg filler metal. The microstructure and properties of the weld were...SiC p/6061Al alloy composite was welded by using TIG and pulsed-TIG welding (P-TIG) without addition of filler metal, or with addition of Al-Si or Al-Mg filler metal. The microstructure and properties of the weld were investigated with XRD, OM, TEM, and MTS-810 testing system was used to observe the effect of different welding procedure and filler metals on the microstructure and properties of the weld. Thermodynamic of SiC-Al reaction was used to analyze the tendency of the reaction between SiC particle and Al matrix during welding. The results showed that the P-TIG tends to produce less plate-like Al 4C 3 precipitates than TIG; when welding with P-TIG, addition of Al-Si filler metal can not only prevent from formation of Al 4C 3, but also decrease hot crack sensitivity of weld; the tensile strength of joint of adding Al-Si filler metal is higher than that of adding Al-Mg filler metal. The SiC p/6061Al composite can be successfully welded by P-TIG with addition of Al-Si filler metal.展开更多
The rules such as process parameters affecting joint properties and theevolution principle of weld's microstructure have been researched by adopting diffusion weldingprocess to connect SiC_w/6061Al composite. Expe...The rules such as process parameters affecting joint properties and theevolution principle of weld's microstructure have been researched by adopting diffusion weldingprocess to connect SiC_w/6061Al composite. Experimental results show that there exists a criticaltemperature region between solid and liquid phase line of SiC_w/6061Al composite, and the regionwill shrink with the increasing of welding pressure. When diffusion welding occurred under thecritical temperature region, welding joint exhibits bad property of bonding, and the matrix and thereinforcement can't bond effectively. When diffusion welding occurred in the critical temperatureregion, the strength of welding joint changes widely with the variation of welding temperature. Whenwelding temperature varies in 10 deg C, the strength of welding joint will change obviously. Onlywhen welding temperature is higher than the critical temperature region, stable joint properties canbe obtained. Simultaneously the matrix and the reinforcement has better interfacial bonded indiffusion welding interface, and no obvious interface reaction occurred, and thus diffusion weldingof SiC_w/6061 Al composite can be successfully realized.展开更多
基金Projects (50872018, 50902018) supported by the National Natural Science Foundation of ChinaProject (1099043) supported by the Science and Technology in Guangxi Province, ChinaProject (090302005) supported by the Basic Research Fund for Northeastern University, China
文摘The mass of high-speed trains can be reduced using the brake disk prepared with SiC network ceramic frame reinforced 6061 aluminum alloy composite （SiCn/Al）. The thermal and stress analyses of SiCn/Al brake disk during emergency braking at a speed of 300 km/h considering airflow cooling were investigated using finite element （FE） and computational fluid dynamics （CFD） methods. All three modes of heat transfer （conduction, convection and radiation） were analyzed along with the design features of the brake assembly and their interfaces. The results suggested that the higher convection coefficients achieved with airflow cooling will not only reduce the maximum temperature in the braking but also reduce the thermal gradients, since heat will be removed faster from hotter parts of the disk. Airflow cooling should be effective to reduce the risk of hot spot formation and disc thermal distortion. The highest temperature after emergency braking was 461 °C and 359 °C without and with considering airflow cooling, respectively. The equivalent stress could reach 269 MPa and 164 MPa without and with considering airflow cooling, respectively. However, the maximum surface stress may exceed the material yield strength during an emergency braking, which may cause a plastic damage accumulation in a brake disk without cooling. The simulation results are consistent with the experimental results well.
文摘SiC p/6061Al alloy composite was welded by using TIG and pulsed-TIG welding (P-TIG) without addition of filler metal, or with addition of Al-Si or Al-Mg filler metal. The microstructure and properties of the weld were investigated with XRD, OM, TEM, and MTS-810 testing system was used to observe the effect of different welding procedure and filler metals on the microstructure and properties of the weld. Thermodynamic of SiC-Al reaction was used to analyze the tendency of the reaction between SiC particle and Al matrix during welding. The results showed that the P-TIG tends to produce less plate-like Al 4C 3 precipitates than TIG; when welding with P-TIG, addition of Al-Si filler metal can not only prevent from formation of Al 4C 3, but also decrease hot crack sensitivity of weld; the tensile strength of joint of adding Al-Si filler metal is higher than that of adding Al-Mg filler metal. The SiC p/6061Al composite can be successfully welded by P-TIG with addition of Al-Si filler metal.
文摘The rules such as process parameters affecting joint properties and theevolution principle of weld's microstructure have been researched by adopting diffusion weldingprocess to connect SiC_w/6061Al composite. Experimental results show that there exists a criticaltemperature region between solid and liquid phase line of SiC_w/6061Al composite, and the regionwill shrink with the increasing of welding pressure. When diffusion welding occurred under thecritical temperature region, welding joint exhibits bad property of bonding, and the matrix and thereinforcement can't bond effectively. When diffusion welding occurred in the critical temperatureregion, the strength of welding joint changes widely with the variation of welding temperature. Whenwelding temperature varies in 10 deg C, the strength of welding joint will change obviously. Onlywhen welding temperature is higher than the critical temperature region, stable joint properties canbe obtained. Simultaneously the matrix and the reinforcement has better interfacial bonded indiffusion welding interface, and no obvious interface reaction occurred, and thus diffusion weldingof SiC_w/6061 Al composite can be successfully realized.
