In situ(TiC+SiC)particles(5 vol.%and 10 vol.%,respectively)-reinforced FeCrCoNi high entropy alloy matrix composites were fabricated via vacuum inductive melting method,with equal volume fractions of TiC and SiC parti...In situ(TiC+SiC)particles(5 vol.%and 10 vol.%,respectively)-reinforced FeCrCoNi high entropy alloy matrix composites were fabricated via vacuum inductive melting method,with equal volume fractions of TiC and SiC particles.X-ray diffraction,scanning electron microscope and energy diffraction spectrum were employed to analyze the microstructure and composi-tion of the samples.The results manifested that the FeCrCoNi matrix is composed of FCC phase,and the in situ particles are homogeneously scattered in the matrix.The presence of reinforcements augmented the ultimate tensile strength from 452 to 783 MPa,and raised the yield strength from 162 to 466 MPa at room temperature,whereas the elongation to fracture was reduced from 70.6%to 28.6%.All the tensile fracture surfaces consisted of numerous tiny dimples,indicating that the composites exhibited ductile fracture.Furthermore,the enhancement of strength ascribes to a combination of thermal mis-match strengthening,load-bearing effect,grain refinement,Orowan strengthening and solid solution strengthening effect,which contribute about 58.0%,2.4%,12.3%,11.1%and 16.2%to the improvement of yield tensile strength,respectively.展开更多
Three types of in-situ TiC(5 vol%,10 vol%and 15 vol%)reinforced high entropy alloy CoCrFeNi matrix composites were produced by vacuum induction smelting.The effect of two extreme cooling conditions(i.e.,slow cooling i...Three types of in-situ TiC(5 vol%,10 vol%and 15 vol%)reinforced high entropy alloy CoCrFeNi matrix composites were produced by vacuum induction smelting.The effect of two extreme cooling conditions(i.e.,slow cooling in fu rnace and rapid cooling in copper crucible)upon the microstructure and mechanical properties was examined.In the case of slow cooling in the furnace,TiC was found to form mostly along the grain boundaries for the 5 vol%samples.With the increase of TiC reinforcements,fibrous TiC appeared and extended into the matrix,leading to an increase in hardness.The ultimate tensile strength of the composites shows a marked variation with increasing TiC content;that is,425.6 MPa(matrix),372.8 MPa(5 vol%),550.4 MPa(10 vol%)and 334.3 MPa(15 vol%),while the elongation-to-failure(i.e.,ductility)decreases.The fracture pattern was found to transit from the ductile to cleavage fracture,as the TiC content increased.When the samples cooled rapidly in copper crucible,the TiC particles formed both along the grain boundaries and within the grains.With the increase of TiC volume fraction,both the hardness and ultimate tensile strength of the resulting composites improved steadily while the elongation-to-failure declined.Therefore,the fast cooling can be used to drastically improve the strength of in-situ TiC reinforced CoCrFeNi.For example,for the 15 vol%TiC/CoCrFeNi composite cooled in the copper crucible,the hardness and ultimate tensile strength can reach as high as 595 HV and 941.7 MPa,respectively.展开更多
V_(x)FeCoNiCu high entropy alloy matrix composites reinforced by in situ TiC particles(10 vol.%),i.e.,V_(x)FeCoNiCu/TiC composites,were fabricated from V–Fe–Co–Ni–Cu–Ti–C system using vacuum inductive melting me...V_(x)FeCoNiCu high entropy alloy matrix composites reinforced by in situ TiC particles(10 vol.%),i.e.,V_(x)FeCoNiCu/TiC composites,were fabricated from V–Fe–Co–Ni–Cu–Ti–C system using vacuum inductive melting method.With the content of vanadium increasing,the size of TiC particles decreased gradually.Meanwhile,vanadium agglomeration occurred slightly.The reaction mechanism of the mixed powder(Fe,V,Ti and C)and the mechanical properties of obtaining V_(x)FeCoNiCu/TiC composites were studied.It was found that three reactions occurred(Fe-Ti-FeTi-Fe_(2)Ti,FeTi-Fe_(2)Ti-Fe-Ti and Ti-C-TiC)in the heating process.The apparent activation energy for these three reactions was calculated and found to be 26.4,698.3 and 1879.0 kJ/mol,respectively.At room temperature,tensile strength and elongation increased first and then decreased with the increase in vanadium content and the microhardness increased gradually.The maximum tensile strength of the composites was determined to be 666 MPa,representing a 17.7%increase over that of FeCoNiCu/TiC high entropy alloy composites.展开更多
The biological materials evolved in nature generally exhibit interpenetrating network structures,which may offer useful inspiration for the architectural design of wear-resistant composites.Here,a strategy for designi...The biological materials evolved in nature generally exhibit interpenetrating network structures,which may offer useful inspiration for the architectural design of wear-resistant composites.Here,a strategy for designing self-lubricating medium entropy alloy(MEA)composites with high strength and excellent anti-wear performance was proposed through quasi-continuously networked in-situ carbides and graphene nanosheets.The discontinuous coating of graphene on the MEA powder surface inhibits continuous metallurgy bonding of the MEA powders during sintering,generating the typical quasi-continuously networked architecture.A good combination of mechanical properties with high fracture strength over 2 GPa and large compressive plasticity over 30%benefits from metallurgy bonding that prevents crack initiation and extension.The wear rate of an order of 10^(−6) m^(3)·N^(−1)·m^(−1) ascribing to an amorphous-crystalline nanocomposite surface,tribo-film induced by graphene,as well as the gradient worn subsurface during friction was achieved by the MEA composite,which is an order of magnitude lower than the unreinforced MEA matrix.展开更多
We extend basic entropies in the classical information theory to matrix ones in the quantum information theory. Then we show that relations between matrix entropies similar to the classical ones hold.
基金the National Undergraduate Training Program for Innovation and Entrepreneurship(No.201910288094Z)This work was also supported by the National Natural Science Foundation of China(51571118,51371098)Jiangsu Province Science and Technology Plan Project(BE2018753/KJ185629).
文摘In situ(TiC+SiC)particles(5 vol.%and 10 vol.%,respectively)-reinforced FeCrCoNi high entropy alloy matrix composites were fabricated via vacuum inductive melting method,with equal volume fractions of TiC and SiC particles.X-ray diffraction,scanning electron microscope and energy diffraction spectrum were employed to analyze the microstructure and composi-tion of the samples.The results manifested that the FeCrCoNi matrix is composed of FCC phase,and the in situ particles are homogeneously scattered in the matrix.The presence of reinforcements augmented the ultimate tensile strength from 452 to 783 MPa,and raised the yield strength from 162 to 466 MPa at room temperature,whereas the elongation to fracture was reduced from 70.6%to 28.6%.All the tensile fracture surfaces consisted of numerous tiny dimples,indicating that the composites exhibited ductile fracture.Furthermore,the enhancement of strength ascribes to a combination of thermal mis-match strengthening,load-bearing effect,grain refinement,Orowan strengthening and solid solution strengthening effect,which contribute about 58.0%,2.4%,12.3%,11.1%and 16.2%to the improvement of yield tensile strength,respectively.
基金This work was supported financially by the National Natural Science Foundation of China(Nos.51571118 and 51371098)the Natural Science Foundation of Jiangsu Province,China(No.BK20141308)Jiangsu province Science and Technology Plan Project,China(No.BE2018753/KJ185629).
文摘Three types of in-situ TiC(5 vol%,10 vol%and 15 vol%)reinforced high entropy alloy CoCrFeNi matrix composites were produced by vacuum induction smelting.The effect of two extreme cooling conditions(i.e.,slow cooling in fu rnace and rapid cooling in copper crucible)upon the microstructure and mechanical properties was examined.In the case of slow cooling in the furnace,TiC was found to form mostly along the grain boundaries for the 5 vol%samples.With the increase of TiC reinforcements,fibrous TiC appeared and extended into the matrix,leading to an increase in hardness.The ultimate tensile strength of the composites shows a marked variation with increasing TiC content;that is,425.6 MPa(matrix),372.8 MPa(5 vol%),550.4 MPa(10 vol%)and 334.3 MPa(15 vol%),while the elongation-to-failure(i.e.,ductility)decreases.The fracture pattern was found to transit from the ductile to cleavage fracture,as the TiC content increased.When the samples cooled rapidly in copper crucible,the TiC particles formed both along the grain boundaries and within the grains.With the increase of TiC volume fraction,both the hardness and ultimate tensile strength of the resulting composites improved steadily while the elongation-to-failure declined.Therefore,the fast cooling can be used to drastically improve the strength of in-situ TiC reinforced CoCrFeNi.For example,for the 15 vol%TiC/CoCrFeNi composite cooled in the copper crucible,the hardness and ultimate tensile strength can reach as high as 595 HV and 941.7 MPa,respectively.
基金the Jiangsu Province Science and Technology Plan Project(No.BE2018753/KJ185629)the National Natural Science Foundation of China(Nos.51571118 and 51371098).
文摘V_(x)FeCoNiCu high entropy alloy matrix composites reinforced by in situ TiC particles(10 vol.%),i.e.,V_(x)FeCoNiCu/TiC composites,were fabricated from V–Fe–Co–Ni–Cu–Ti–C system using vacuum inductive melting method.With the content of vanadium increasing,the size of TiC particles decreased gradually.Meanwhile,vanadium agglomeration occurred slightly.The reaction mechanism of the mixed powder(Fe,V,Ti and C)and the mechanical properties of obtaining V_(x)FeCoNiCu/TiC composites were studied.It was found that three reactions occurred(Fe-Ti-FeTi-Fe_(2)Ti,FeTi-Fe_(2)Ti-Fe-Ti and Ti-C-TiC)in the heating process.The apparent activation energy for these three reactions was calculated and found to be 26.4,698.3 and 1879.0 kJ/mol,respectively.At room temperature,tensile strength and elongation increased first and then decreased with the increase in vanadium content and the microhardness increased gradually.The maximum tensile strength of the composites was determined to be 666 MPa,representing a 17.7%increase over that of FeCoNiCu/TiC high entropy alloy composites.
基金the National Natural Science Foundation of China(52175188,52274367)Guangdong Basic and Applied Basic Research Foundation(No.2024A1515012378)+2 种基金Key Research and Development Program of Shaanxi Province(2023-YBGY-434)Open Fund of Liaoning Provincial Key Laboratory of Aero-engine Materials Tribology(LKLAMTF202301)the Science and Technology on Reactor System Design Technology Laboratory and the Fundamental Research Funds for the Central Universities.
文摘The biological materials evolved in nature generally exhibit interpenetrating network structures,which may offer useful inspiration for the architectural design of wear-resistant composites.Here,a strategy for designing self-lubricating medium entropy alloy(MEA)composites with high strength and excellent anti-wear performance was proposed through quasi-continuously networked in-situ carbides and graphene nanosheets.The discontinuous coating of graphene on the MEA powder surface inhibits continuous metallurgy bonding of the MEA powders during sintering,generating the typical quasi-continuously networked architecture.A good combination of mechanical properties with high fracture strength over 2 GPa and large compressive plasticity over 30%benefits from metallurgy bonding that prevents crack initiation and extension.The wear rate of an order of 10^(−6) m^(3)·N^(−1)·m^(−1) ascribing to an amorphous-crystalline nanocomposite surface,tribo-film induced by graphene,as well as the gradient worn subsurface during friction was achieved by the MEA composite,which is an order of magnitude lower than the unreinforced MEA matrix.
文摘We extend basic entropies in the classical information theory to matrix ones in the quantum information theory. Then we show that relations between matrix entropies similar to the classical ones hold.
