To investigate the worn-surface microstructure and fatigue cracks in D2 wheel steel under the pure rolling and 0.5% slip ratio conditions,a rolling wear test using a GPM-40 wear machine to simulate the wheel/rail oper...To investigate the worn-surface microstructure and fatigue cracks in D2 wheel steel under the pure rolling and 0.5% slip ratio conditions,a rolling wear test using a GPM-40 wear machine to simulate the wheel/rail operation was performed. After testing,a transmission electron microscope,a scanning electron microscope with electron backscatter diffraction,and micro-hardness testers were used to characterize the microstructure and fatigue cracks.The surface microstrncture and hardness of the pure rolling sample were in a steady state after 8 × 10^4 cycles;however,the 0.5% slip ratio sample reached a steady state after 7 × 10^3 cycles.Regardless of whether the test uses the slip ratio,the orientation of lamellar pearlites gradually became parallel to the surface and a portion of lamellar cementites was fragmented and dissolved during the formation of steady-state microstructure.The slip ratio accelerates this process.The hardening mechanism of the samples shows a decrease in the lamellar spacing of pearlite and the refinement of proeutectoid ferrite (PF).As the number of cycles increased,plastic deformation of samples became increasingly severe and the wear mechanism of the samples was fatigue wear in steady state.The sample surfaces formed shallow cracks,which gradually peeled off.The slip ratio accelerated the initiation and propagation of fatigue cracks because of the high friction stress on the contact surface.Most fatigue cracks initiated at the interface of pearlite and PF and in the PF region.展开更多
通过显微维氏硬度计、电子背散射衍射和透射电子显微镜等分析手段研究了不同电流密度对单晶铜棒材电化学冷拉拔过程中拉拔力、硬度、晶体取向及位错的影响。结果表明,当电流密度为6.7 m A·cm^(-2)时,激活的滑移系数量最多,拉拔力最...通过显微维氏硬度计、电子背散射衍射和透射电子显微镜等分析手段研究了不同电流密度对单晶铜棒材电化学冷拉拔过程中拉拔力、硬度、晶体取向及位错的影响。结果表明,当电流密度为6.7 m A·cm^(-2)时,激活的滑移系数量最多,拉拔力最小,且拉拔后棒材的表面硬度也最小。不同的电流密度使单晶铜棒材的塑化程度不同,其主要原因是由于晶体内滑移系激活数量不同引起,导致位错易于运动,使得位错缠结减少。而在更高的电流密度下,由于表面腐蚀层厚度的增加,激活的滑移系数量减少,继而摩擦力增大,位错密度增大,使得拉拔力再次增大。展开更多
As one of the longest strike-slip fault in Asia,the Altyn Tagh Fault（ATF）defines the northern boundary of the Tibetan Plateau and plays a significant role inaccommodating the deformation resulting from the IndiaAsia...As one of the longest strike-slip fault in Asia,the Altyn Tagh Fault（ATF）defines the northern boundary of the Tibetan Plateau and plays a significant role inaccommodating the deformation resulting from the IndiaAsia convergence.展开更多
文摘To investigate the worn-surface microstructure and fatigue cracks in D2 wheel steel under the pure rolling and 0.5% slip ratio conditions,a rolling wear test using a GPM-40 wear machine to simulate the wheel/rail operation was performed. After testing,a transmission electron microscope,a scanning electron microscope with electron backscatter diffraction,and micro-hardness testers were used to characterize the microstructure and fatigue cracks.The surface microstrncture and hardness of the pure rolling sample were in a steady state after 8 × 10^4 cycles;however,the 0.5% slip ratio sample reached a steady state after 7 × 10^3 cycles.Regardless of whether the test uses the slip ratio,the orientation of lamellar pearlites gradually became parallel to the surface and a portion of lamellar cementites was fragmented and dissolved during the formation of steady-state microstructure.The slip ratio accelerates this process.The hardening mechanism of the samples shows a decrease in the lamellar spacing of pearlite and the refinement of proeutectoid ferrite (PF).As the number of cycles increased,plastic deformation of samples became increasingly severe and the wear mechanism of the samples was fatigue wear in steady state.The sample surfaces formed shallow cracks,which gradually peeled off.The slip ratio accelerated the initiation and propagation of fatigue cracks because of the high friction stress on the contact surface.Most fatigue cracks initiated at the interface of pearlite and PF and in the PF region.
文摘通过显微维氏硬度计、电子背散射衍射和透射电子显微镜等分析手段研究了不同电流密度对单晶铜棒材电化学冷拉拔过程中拉拔力、硬度、晶体取向及位错的影响。结果表明,当电流密度为6.7 m A·cm^(-2)时,激活的滑移系数量最多,拉拔力最小,且拉拔后棒材的表面硬度也最小。不同的电流密度使单晶铜棒材的塑化程度不同,其主要原因是由于晶体内滑移系激活数量不同引起,导致位错易于运动,使得位错缠结减少。而在更高的电流密度下,由于表面腐蚀层厚度的增加,激活的滑移系数量减少,继而摩擦力增大,位错密度增大,使得拉拔力再次增大。
基金supported by the National Natural Sciences Foundation of China(Grants No.41202156 and 41330211)China Geological Survey(Grants No.12120115026901 and 12120115027001)the Institute of Geology,CAGS(Grant No.J1520)
文摘As one of the longest strike-slip fault in Asia,the Altyn Tagh Fault（ATF）defines the northern boundary of the Tibetan Plateau and plays a significant role inaccommodating the deformation resulting from the IndiaAsia convergence.
