The retrogression and re-aging(RRA)processes,aimed mainly at tailoring intergranular precipitates,could significantly improve the corrosion resistance(i.e.,stress corrosion cracking resistance)without considerably dec...The retrogression and re-aging(RRA)processes,aimed mainly at tailoring intergranular precipitates,could significantly improve the corrosion resistance(i.e.,stress corrosion cracking resistance)without considerably decreasing the strength,which signifies that an efficient control of the size,distribution and evolution of intergranular and intragranular precipitates becomes critical for the integrated properties of the(mid-)thick high-strength Al alloy plates.Compared to RRA process with retrogression at200℃ (T77),this study investigated the impact of a modified RRA process(MT77)with lower retrogression temperatures(155-175℃ )and first-stage under-aging on the properties of a high-strength AA7050 Al alloy,in combination with detailed precipitate characterization.The study showed that the strength/microhardness of the RRA-treated alloys decreased with raising retrogression temperature and/or prolonging retrogression time,along with the increased electrical conductivity.The rapid responsiveness of microstructure/property typical of retrogression at 200℃ was obviously postponed or decreased by using MT77 process with longer retrogression time that was more suitable for treating the(mid-)thick plates.On the other hand,higher retrogression temperature facilitated more intragranularηprecipitates,coarse intergranular precipitates and wide precipitate free zones,which prominently increased the electrical conductivity alongside a considerable strength loss as compared to the MT77-treated alloys.With the preferred MT77 process,the high strength approaching T6 level as well as good corrosion resistance was achieved.However,though a relatively homogeneous through-thickness strength was obtained,some small discrepancies of properties between the central and surface areas of an 86-mm thick 7050 Al alloy plate were observed,possibly related to the quenching sensitivity.The precipitate evolution and mechanistic connection to the properties were discussed and reviewed for high-strength Al alloys along with suggestions for fu展开更多
基于科学级CCD相机的多色光度测量技术凭借着实用性强、简单有效等特点在天文观测中受到了广泛应用。针对传统多色测光技术缺乏同时性这一问题,本文介绍了一种新型的同时性三通道测光系统,采用分色的设计方式实现了Sloan Digital Sky Su...基于科学级CCD相机的多色光度测量技术凭借着实用性强、简单有效等特点在天文观测中受到了广泛应用。针对传统多色测光技术缺乏同时性这一问题,本文介绍了一种新型的同时性三通道测光系统,采用分色的设计方式实现了Sloan Digital Sky Survey(SDSS)测光标准g′,r′和i′三个波段分光。首先,利用Zemax软件对三通道光度计的光学系统进行了仿真分析,仿真结果显示该系统符合总体设计指标且能够满足使用要求。然后,为验证该系统的光学性能,我们针对大量SDSS标准星开展观测,实测结果表明该设备在g′,r′和i′三个通道的视场分别为21.5′×21.5′,21.5′×21.5′和21.3′×21.3′,系统效率分别为65.6%,68.3%和63.7%,将曝光时间归算为1 s、信噪比为5时,计算得出的极限探测星等分别为15.26,16.39和15.63。接下来可通过对系统的优化,进一步提高其极限星等的探测能力。展开更多
The maximum velocity of a mobile vortex in movement is generally limited by the phenomenon of flux-flow instability(FFI),which necessitates weak vortex pinning and fast heat removal from non-equilibrium electrons.We h...The maximum velocity of a mobile vortex in movement is generally limited by the phenomenon of flux-flow instability(FFI),which necessitates weak vortex pinning and fast heat removal from non-equilibrium electrons.We here demonstrate exfoliations and nano-fabrications of Bi_(2)Sr_(2)Ca_(2)Cu_(3)O_(10+δ) crystalline nanostrips,which possess a rather weak pinning volume of vortices,relatively low resistivity,and large normal electron diffusion coefficient.The deduced vortex velocity in Bi_(2)Sr_(2)Ca_(2)Cu_(3)O_(10+δ) crystalline nanostrips can be up to 300 km/s near the superconducting transition temperature,well above the speed of sound.The observed vortex velocity is an order of magnitude faster than that of conventional superconducting systems,representing a perfect platform for exploration of ultra-fast vortex matter and a good candidate for fabrications of superconducting nanowire single photon detectors or superconducting THz modulator.展开更多
基金financial support from the Constructed Project for Key Laboratory of Beijing,China(No.BJSJ2019004)the State Key Laboratory for Advanced Metals and Materials of China(No.2018Z-23)+2 种基金the Major State Research and Development Program of China(No.2016YFB0300801)the National Natural Science Foundation of China(No.51401016)the supports from International S&T Cooperation Projects of Nanjing,China(No.201818014)。
文摘The retrogression and re-aging(RRA)processes,aimed mainly at tailoring intergranular precipitates,could significantly improve the corrosion resistance(i.e.,stress corrosion cracking resistance)without considerably decreasing the strength,which signifies that an efficient control of the size,distribution and evolution of intergranular and intragranular precipitates becomes critical for the integrated properties of the(mid-)thick high-strength Al alloy plates.Compared to RRA process with retrogression at200℃ (T77),this study investigated the impact of a modified RRA process(MT77)with lower retrogression temperatures(155-175℃ )and first-stage under-aging on the properties of a high-strength AA7050 Al alloy,in combination with detailed precipitate characterization.The study showed that the strength/microhardness of the RRA-treated alloys decreased with raising retrogression temperature and/or prolonging retrogression time,along with the increased electrical conductivity.The rapid responsiveness of microstructure/property typical of retrogression at 200℃ was obviously postponed or decreased by using MT77 process with longer retrogression time that was more suitable for treating the(mid-)thick plates.On the other hand,higher retrogression temperature facilitated more intragranularηprecipitates,coarse intergranular precipitates and wide precipitate free zones,which prominently increased the electrical conductivity alongside a considerable strength loss as compared to the MT77-treated alloys.With the preferred MT77 process,the high strength approaching T6 level as well as good corrosion resistance was achieved.However,though a relatively homogeneous through-thickness strength was obtained,some small discrepancies of properties between the central and surface areas of an 86-mm thick 7050 Al alloy plate were observed,possibly related to the quenching sensitivity.The precipitate evolution and mechanistic connection to the properties were discussed and reviewed for high-strength Al alloys along with suggestions for fu
文摘基于科学级CCD相机的多色光度测量技术凭借着实用性强、简单有效等特点在天文观测中受到了广泛应用。针对传统多色测光技术缺乏同时性这一问题,本文介绍了一种新型的同时性三通道测光系统,采用分色的设计方式实现了Sloan Digital Sky Survey(SDSS)测光标准g′,r′和i′三个波段分光。首先,利用Zemax软件对三通道光度计的光学系统进行了仿真分析,仿真结果显示该系统符合总体设计指标且能够满足使用要求。然后,为验证该系统的光学性能,我们针对大量SDSS标准星开展观测,实测结果表明该设备在g′,r′和i′三个通道的视场分别为21.5′×21.5′,21.5′×21.5′和21.3′×21.3′,系统效率分别为65.6%,68.3%和63.7%,将曝光时间归算为1 s、信噪比为5时,计算得出的极限探测星等分别为15.26,16.39和15.63。接下来可通过对系统的优化,进一步提高其极限星等的探测能力。
基金supporting high quality of post growth treatment Bi_(2)Sr_(2)Ca_(2)Cu_(3)O_(10+δ)single crystalssupported by the National Key Research and Development Program of China(Grant No.2017YFA0304000)+4 种基金the National Natural Science Foundation of China(Grant Nos.61971408 and 61827823)Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)Shanghai Rising-Star Program(Grant No.20QA1410900)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant Nos.2020241 and 2021230)the Natural Science Foundation of Shanghai(Grant No.19ZR1467400)。
文摘The maximum velocity of a mobile vortex in movement is generally limited by the phenomenon of flux-flow instability(FFI),which necessitates weak vortex pinning and fast heat removal from non-equilibrium electrons.We here demonstrate exfoliations and nano-fabrications of Bi_(2)Sr_(2)Ca_(2)Cu_(3)O_(10+δ) crystalline nanostrips,which possess a rather weak pinning volume of vortices,relatively low resistivity,and large normal electron diffusion coefficient.The deduced vortex velocity in Bi_(2)Sr_(2)Ca_(2)Cu_(3)O_(10+δ) crystalline nanostrips can be up to 300 km/s near the superconducting transition temperature,well above the speed of sound.The observed vortex velocity is an order of magnitude faster than that of conventional superconducting systems,representing a perfect platform for exploration of ultra-fast vortex matter and a good candidate for fabrications of superconducting nanowire single photon detectors or superconducting THz modulator.
