A series of Co/Si/(Co/Cu/Co) multilayers and Co/Si/Co sandwiches were prepared by high vacuum (electron-beam) evaporation. It was found that a Si spacer (≥0.9nm) could greatly decrease the interlayer coupling in Co...A series of Co/Si/(Co/Cu/Co) multilayers and Co/Si/Co sandwiches were prepared by high vacuum (electron-beam) evaporation. It was found that a Si spacer (≥0.9nm) could greatly decrease the interlayer coupling in Co/Si/Co sandwiches and there was no magnetoresistance(MR) or spin-valve MR in them due to the high resistivity of Si spacer. While in Co/Si/(Co/Cu/Co) multilayers, we observed a spin-valve MR of about (0.5%) through a (nominal) 2.7nm Si spacer at room temperature. The spin-valve MR in Co/Si/(Co/Cu/Co) multilayers was attributed to the enhanced spin polarization of conduction electrons caused by the top Co/Cu/Co sandwich with GMR mechanism and high spin-dependent scattering at Co/Cu interface.展开更多
To address the zero-sample challenge in preparation parameter design for newly developed alloys,a novel machine learning strategy that integrates basic dataset construction with Bayesian optimization,was proposed.The ...To address the zero-sample challenge in preparation parameter design for newly developed alloys,a novel machine learning strategy that integrates basic dataset construction with Bayesian optimization,was proposed.The impact of basic sample dataset construction methods,optimization benchmarks and multi-objective utility functions on Bayesian optimization was investigated.It was found that the combination of orthogonal design,linear benchmark,and shifted multiplicative utility function exhibits the best optimization performance.The strategy was then applied to a new Cu-Ni-Co-Si alloy with ultra-low Co content(0.7 wt.%Co),previously designed by our research team.Rapid optimization of six preparation parameters in the two-stage deformation and aging process of the zero-sample alloy was achieved through only 23 experiments.The measured ultimate tensile strength and electrical conductivity of the new alloy were 878 MPa and 44.0%(IACS),respectively,reaching the comprehensive performance level of the Cu-Ni-Co-Si alloy(C70350 alloy)containing 1.0-2.0 wt.%Co.展开更多
A Cu-1.9Ni-1.9Co-0.9Si(mass fraction,%)alloy with high strength and electrical conductivity was designed by cluster formula approach.The microstructure evolution of the alloy during thermomechanical treatment was syst...A Cu-1.9Ni-1.9Co-0.9Si(mass fraction,%)alloy with high strength and electrical conductivity was designed by cluster formula approach.The microstructure evolution of the alloy during thermomechanical treatment was systematically investigated.The strengthening mechanism and electrical conductivity of the alloy were discussed in detail.The optimal thermomechanical treatment process was as follows:solid solution→80%cold rolling→(450℃,4 h)aging→50%cold rolling→(400℃,4 h)aging.The designed alloy achieved excellent comprehensive properties with a microhardness of HV 260,a yield strength of 843 MPa,a tensile strength of 884 MPa,and an electrical conductivity of 42.6%(IACS).Compared to direct aging treatment,the designed alloy subjected to multi-stage thermomechanical treatment had refined grains,high density of dislocations,and accelerated of precipitation of(Ni,Co)_(2)Si precipitates.High strength was mainly attributed to the combined effect of dislocation strengthening,work hardening and sub-grain strengthening,while good electrical conductivity was maintained through the precipitation of the large number of nanoparticles.展开更多
文摘A series of Co/Si/(Co/Cu/Co) multilayers and Co/Si/Co sandwiches were prepared by high vacuum (electron-beam) evaporation. It was found that a Si spacer (≥0.9nm) could greatly decrease the interlayer coupling in Co/Si/Co sandwiches and there was no magnetoresistance(MR) or spin-valve MR in them due to the high resistivity of Si spacer. While in Co/Si/(Co/Cu/Co) multilayers, we observed a spin-valve MR of about (0.5%) through a (nominal) 2.7nm Si spacer at room temperature. The spin-valve MR in Co/Si/(Co/Cu/Co) multilayers was attributed to the enhanced spin polarization of conduction electrons caused by the top Co/Cu/Co sandwich with GMR mechanism and high spin-dependent scattering at Co/Cu interface.
基金supported by the National Natural Science Foundation of China(Nos.52404387,52090041,52374379,52425409)Xiaomi Young Scholars Program China,the National Postdoctoral Program for Innovative Talents,China(No.BX20230042)China Postdoctoral Science Foundation(No.2024M750174)。
文摘To address the zero-sample challenge in preparation parameter design for newly developed alloys,a novel machine learning strategy that integrates basic dataset construction with Bayesian optimization,was proposed.The impact of basic sample dataset construction methods,optimization benchmarks and multi-objective utility functions on Bayesian optimization was investigated.It was found that the combination of orthogonal design,linear benchmark,and shifted multiplicative utility function exhibits the best optimization performance.The strategy was then applied to a new Cu-Ni-Co-Si alloy with ultra-low Co content(0.7 wt.%Co),previously designed by our research team.Rapid optimization of six preparation parameters in the two-stage deformation and aging process of the zero-sample alloy was achieved through only 23 experiments.The measured ultimate tensile strength and electrical conductivity of the new alloy were 878 MPa and 44.0%(IACS),respectively,reaching the comprehensive performance level of the Cu-Ni-Co-Si alloy(C70350 alloy)containing 1.0-2.0 wt.%Co.
基金the financial support by the National Natural Science Foundation of China(No.U2202255)the Hunan Provincial Natural Science Foundation of China(No.2024JJ2076)the Key Research and Development Program of Ningbo,China(No.2023Z092)。
文摘A Cu-1.9Ni-1.9Co-0.9Si(mass fraction,%)alloy with high strength and electrical conductivity was designed by cluster formula approach.The microstructure evolution of the alloy during thermomechanical treatment was systematically investigated.The strengthening mechanism and electrical conductivity of the alloy were discussed in detail.The optimal thermomechanical treatment process was as follows:solid solution→80%cold rolling→(450℃,4 h)aging→50%cold rolling→(400℃,4 h)aging.The designed alloy achieved excellent comprehensive properties with a microhardness of HV 260,a yield strength of 843 MPa,a tensile strength of 884 MPa,and an electrical conductivity of 42.6%(IACS).Compared to direct aging treatment,the designed alloy subjected to multi-stage thermomechanical treatment had refined grains,high density of dislocations,and accelerated of precipitation of(Ni,Co)_(2)Si precipitates.High strength was mainly attributed to the combined effect of dislocation strengthening,work hardening and sub-grain strengthening,while good electrical conductivity was maintained through the precipitation of the large number of nanoparticles.
