The application of single-phase face-centered cubic(FCC)medium entropy alloys(MEAs)in the engi-neering industry is often hindered by the challenge of insufficient strength.In this study,a novel non-equiatomic ratio Ni...The application of single-phase face-centered cubic(FCC)medium entropy alloys(MEAs)in the engi-neering industry is often hindered by the challenge of insufficient strength.In this study,a novel non-equiatomic ratio Ni_(40)Co_(30)Cr_(20)Al_(5)Ti_(5)MEA was successfully fabricated.Through the well-designed mechan-ical heat treatment processing,we introduced a heterogeneous grain structure comprising 67.4%fine grain and 32.6%coarse grain.Additionally,heterogeneous size L12 phases consisting of 18.7%submicron precip-itates and 11.7%nano-sized precipitates,were incorporated into the alloy.Tensile tests conducted at room temperature revealed that the double heterogeneous structure alloy demonstrated remarkable strength–ductility synergy.It exhibited a yield strength of 1200 MPa,an ultimate tensile strength of 1560 MPa and a total elongation of 33.6%.The exceptional strength of the alloy can be primarily attributed to heteroge-neous deformation induced strengthening,grain boundary strengthening and precipitation strengthening.The excellent ductility is mainly attributed to the high-density stacking faults and Lomer–Cottrell locks.This study not only contributes to the clarification of the strengthening and deformation mechanism of double heterogeneous structure alloys but also provides an effective strategy for the development of high-performance alloys with high strength and ductility.展开更多
Precipitation strengthening provides one of the most widely-used mechanisms for strengthen-ing multi-principal-element alloys(MPEAs).Here,we report dual-morphology B2 precipitates in Co_(36)Cr_(15)Fe_(18)Ni_(18)Al_(8)...Precipitation strengthening provides one of the most widely-used mechanisms for strengthen-ing multi-principal-element alloys(MPEAs).Here,we report dual-morphology B2 precipitates in Co_(36)Cr_(15)Fe_(18)Ni_(18)Al_(8)Ti_(4)Mo_(1)MPEA obtained by thermo-mechanical processing.Electron microscopy charac-terization reveals that the dual-morphology B2 precipitates are either recrystallized B2 particles formed at the grain boundaries or triple junctions with recrystallization process,or rod-like within the non-recrystallized FCC matrix.The dual-morphology B2 precipitates enhance the yield strength and ultimate tensile strength up to 1120 MPa and 1480 MPa,respectively.This work suggests the mechanical proper-ties of the alloy can be optimized by B2 precipitation strengthening to meet the needs of engineering applications.展开更多
Developing high-performance alloys with gigapascal strength and excellent ductility is crucial for modern engineering applications.The concept of multi-component high/medium entropy alloys(H/MEAs)provides an innovativ...Developing high-performance alloys with gigapascal strength and excellent ductility is crucial for modern engineering applications.The concept of multi-component high/medium entropy alloys(H/MEAs)provides an innovative approach to designing such alloys.In this work,we developed the Co_(1.5)CrNi_(1.5)Al_(0.2)Ti_(0.2)MEA,which exhibits outstanding mechanical properties at room temperature through low-temperature pre-aging followed by annealing treatment.Tensile testing reveals that the MEA possesses an ultrahigh yield strength of 20±0785 MPa,an ultimate tensile strength of 2365±70 MPa,and exceptional ductility of 15.8%±1.7%.The superior tensile properties are attributed to the formation of fully recrystal-lized heterogeneous structures(HGS)composed of ultrafine grain(UFG)and fine grain(FG)regions,along with discontinuous precipitation of coherent nano-size lamellar L1_(2)precipitates.The mechanical incompatibility between the UFG region and the FG regions during deformation induces the accumulation of a large number of geometrically necessary dislocations at the interface,resulting in strain distribution and hetero-deformation-induced(HDI)stress accumulation,contributing significantly to HDI strengthening.HDI strengthening,precipitation strengthening,and grain boundary strengthening are the primary mechanisms responsible for the ultra-high yield strength of the MEA.During deformation,the dominant deformation mechanisms include dislocation slip,deformation-induced stacking faults,and Lomer-Cottrell locks,with minor deformation twinning.The synergistic interaction of these multiple deformation modes provides the MEA with excellent work hardening capability,delaying plastic instability and achieving an excellent combination of strength and ductility.This study provides an effective strategy for synergistically strengthening MEAs by combining HDI strengthening with traditional strengthening mechanisms.These findings pave the way for the development of advanced structural materials with high performance tailored for demanding applications in engineering.展开更多
We report the experimental results of the commissioning phase in the 10 PW laser beamline of the Shanghai Superintense Ultrafast Laser Facility(SULF).The peak power reaches 2.4 PW on target without the last amplifying...We report the experimental results of the commissioning phase in the 10 PW laser beamline of the Shanghai Superintense Ultrafast Laser Facility(SULF).The peak power reaches 2.4 PW on target without the last amplifying during the experiment.The laser energy of 72±9 J is directed to a focal spot of approximately 6μm diameter(full width at half maximum)in 30 fs pulse duration,yielding a focused peak intensity around 2.0×10^(21)W/cm^(2).The first laser-proton acceleration experiment is performed using plain copper and plastic targets.High-energy proton beams with maximum cut-off energy up to 62.5 MeV are achieved using copper foils at the optimum target thickness of 4μm via target normal sheath acceleration.For plastic targets of tens of nanometers thick,the proton cut-off energy is approximately 20 MeV,showing ring-like or flamented density distributions.These experimental results reflect the capabilities of the SULF-10 PW beamline,for example,both ultrahigh intensity and relatively good beam contrast.Further optimization for these key parameters is underway,where peak laser intensities of 10^(22)-10^(23)w/cm^(2)are anticipated to support various experiments on extreme field physics.展开更多
We report on experimental observation of non-laminar proton acceleration modulated by a strong magnetic field in laser irradiating micrometer aluminum targets.The results illustrate the coexistence of ring-like and fi...We report on experimental observation of non-laminar proton acceleration modulated by a strong magnetic field in laser irradiating micrometer aluminum targets.The results illustrate the coexistence of ring-like and filamentation structures.We implement the knife edge method into the radiochromic film detector to map the accelerated beams,measuring a source size of 30-110μm for protons of more than 5 MeV.The diagnosis reveals that the ring-like profile originates from low-energy protons far off the axis whereas the filamentation is from the near-axis high-energy protons,exhibiting non-laminar features.Particle-in-cell simulations reproduced the experimental results,showing that the short-term magnetic turbulence via Weibel instability and the long-term quasi-static annular magnetic field by the streaming electric current account for the measured beam profile.Our work provides direct mapping of laser-driven proton sources in the space-energy domain and reveals the non-laminar beam evolution at featured time scales.展开更多
基金supported by the National Key R&D Program of China(No.2022YFA1603800)the National Natural Science Foundation of China(No.12274362)the Central Guidance on Local Science and Technology Development Fund of Hebei Province(No.216Z1012G)。
文摘The application of single-phase face-centered cubic(FCC)medium entropy alloys(MEAs)in the engi-neering industry is often hindered by the challenge of insufficient strength.In this study,a novel non-equiatomic ratio Ni_(40)Co_(30)Cr_(20)Al_(5)Ti_(5)MEA was successfully fabricated.Through the well-designed mechan-ical heat treatment processing,we introduced a heterogeneous grain structure comprising 67.4%fine grain and 32.6%coarse grain.Additionally,heterogeneous size L12 phases consisting of 18.7%submicron precip-itates and 11.7%nano-sized precipitates,were incorporated into the alloy.Tensile tests conducted at room temperature revealed that the double heterogeneous structure alloy demonstrated remarkable strength–ductility synergy.It exhibited a yield strength of 1200 MPa,an ultimate tensile strength of 1560 MPa and a total elongation of 33.6%.The exceptional strength of the alloy can be primarily attributed to heteroge-neous deformation induced strengthening,grain boundary strengthening and precipitation strengthening.The excellent ductility is mainly attributed to the high-density stacking faults and Lomer–Cottrell locks.This study not only contributes to the clarification of the strengthening and deformation mechanism of double heterogeneous structure alloys but also provides an effective strategy for the development of high-performance alloys with high strength and ductility.
基金supported by the Central Guidance on Local Science and Technology Development Fund of Hebei Province(No.216Z1012G)the National Natural Science Foundation of China(No.12174274).
文摘Precipitation strengthening provides one of the most widely-used mechanisms for strengthen-ing multi-principal-element alloys(MPEAs).Here,we report dual-morphology B2 precipitates in Co_(36)Cr_(15)Fe_(18)Ni_(18)Al_(8)Ti_(4)Mo_(1)MPEA obtained by thermo-mechanical processing.Electron microscopy charac-terization reveals that the dual-morphology B2 precipitates are either recrystallized B2 particles formed at the grain boundaries or triple junctions with recrystallization process,or rod-like within the non-recrystallized FCC matrix.The dual-morphology B2 precipitates enhance the yield strength and ultimate tensile strength up to 1120 MPa and 1480 MPa,respectively.This work suggests the mechanical proper-ties of the alloy can be optimized by B2 precipitation strengthening to meet the needs of engineering applications.
基金supported by the National Key Research and Development Program of China(No.2022YFA1603800)the National Natural Science Foundation of China(No.12274362).
文摘Developing high-performance alloys with gigapascal strength and excellent ductility is crucial for modern engineering applications.The concept of multi-component high/medium entropy alloys(H/MEAs)provides an innovative approach to designing such alloys.In this work,we developed the Co_(1.5)CrNi_(1.5)Al_(0.2)Ti_(0.2)MEA,which exhibits outstanding mechanical properties at room temperature through low-temperature pre-aging followed by annealing treatment.Tensile testing reveals that the MEA possesses an ultrahigh yield strength of 20±0785 MPa,an ultimate tensile strength of 2365±70 MPa,and exceptional ductility of 15.8%±1.7%.The superior tensile properties are attributed to the formation of fully recrystal-lized heterogeneous structures(HGS)composed of ultrafine grain(UFG)and fine grain(FG)regions,along with discontinuous precipitation of coherent nano-size lamellar L1_(2)precipitates.The mechanical incompatibility between the UFG region and the FG regions during deformation induces the accumulation of a large number of geometrically necessary dislocations at the interface,resulting in strain distribution and hetero-deformation-induced(HDI)stress accumulation,contributing significantly to HDI strengthening.HDI strengthening,precipitation strengthening,and grain boundary strengthening are the primary mechanisms responsible for the ultra-high yield strength of the MEA.During deformation,the dominant deformation mechanisms include dislocation slip,deformation-induced stacking faults,and Lomer-Cottrell locks,with minor deformation twinning.The synergistic interaction of these multiple deformation modes provides the MEA with excellent work hardening capability,delaying plastic instability and achieving an excellent combination of strength and ductility.This study provides an effective strategy for synergistically strengthening MEAs by combining HDI strengthening with traditional strengthening mechanisms.These findings pave the way for the development of advanced structural materials with high performance tailored for demanding applications in engineering.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB16)the National Natural Science Foundation of China(Nos.11875307,11935008,11804348,11705260,11905278 and 11975302)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2021242).
文摘We report the experimental results of the commissioning phase in the 10 PW laser beamline of the Shanghai Superintense Ultrafast Laser Facility(SULF).The peak power reaches 2.4 PW on target without the last amplifying during the experiment.The laser energy of 72±9 J is directed to a focal spot of approximately 6μm diameter(full width at half maximum)in 30 fs pulse duration,yielding a focused peak intensity around 2.0×10^(21)W/cm^(2).The first laser-proton acceleration experiment is performed using plain copper and plastic targets.High-energy proton beams with maximum cut-off energy up to 62.5 MeV are achieved using copper foils at the optimum target thickness of 4μm via target normal sheath acceleration.For plastic targets of tens of nanometers thick,the proton cut-off energy is approximately 20 MeV,showing ring-like or flamented density distributions.These experimental results reflect the capabilities of the SULF-10 PW beamline,for example,both ultrahigh intensity and relatively good beam contrast.Further optimization for these key parameters is underway,where peak laser intensities of 10^(22)-10^(23)w/cm^(2)are anticipated to support various experiments on extreme field physics.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB16)National Natural Science Foundation of China(Nos.11875307,11935008,11804348,11705260,11905278,and 11975302)Youth Innovation Promotion Association of the Chinese Academy of Sciences.
文摘We report on experimental observation of non-laminar proton acceleration modulated by a strong magnetic field in laser irradiating micrometer aluminum targets.The results illustrate the coexistence of ring-like and filamentation structures.We implement the knife edge method into the radiochromic film detector to map the accelerated beams,measuring a source size of 30-110μm for protons of more than 5 MeV.The diagnosis reveals that the ring-like profile originates from low-energy protons far off the axis whereas the filamentation is from the near-axis high-energy protons,exhibiting non-laminar features.Particle-in-cell simulations reproduced the experimental results,showing that the short-term magnetic turbulence via Weibel instability and the long-term quasi-static annular magnetic field by the streaming electric current account for the measured beam profile.Our work provides direct mapping of laser-driven proton sources in the space-energy domain and reveals the non-laminar beam evolution at featured time scales.
