Thermal stability,crystallization behavior,Vickers hardness and magnetic properties of the Fe41Co7-xNixCr15Mo14C15B6Y2（x=0,1,3,5） bulk metallic glasses were investigated.The Fe41Co7-xNixCr15Mo14C15B6Y2（x=0,1,3,5） ...Thermal stability,crystallization behavior,Vickers hardness and magnetic properties of the Fe41Co7-xNixCr15Mo14C15B6Y2（x=0,1,3,5） bulk metallic glasses were investigated.The Fe41Co7-xNixCr15Mo14C15B6Y2（x=0,1,3,5） metallic glasses were fabricated by copper mold casting method.The thermal stability and crystallization behavior of the metallic glass rods were investigated by differential scanning calorimetry and isothermal experiments.Hardness measurements for samples annealed at different temperatures for different time were carried out at room temperature by the Vickers hardness tester,and magnetic measurements were performed at different temperatures by the vibrating sample magnetometer.It is shown that the addition of Ni does not play a positive role for enlarging ΔTx and GFA from parameter γ（=Tx/（Tg＋Tl））,and it can,however,increase the activation energy in the initial stage of crystallization by changing the initial crystallization behavior.The minor addition of Ni can refine the crystal grain obtained from the full crystallization experiment.The primary crystallization causes the decrease of hardness in these alloys,and as the crystallization continues,the hardness in all samples increases instead due to the precipitation of carbide and boride.The annealing temperature has an obvious effect on magnetic properties of these alloys,and the minor addition of Ni can effectively prevent the alloy annealed at high temperature to transform from paramagnetic to ferromagnetic state.展开更多
Fe-Cr-Mo-Ni-C-Co alloy was quenched in liquid nitrogen and held for 24 h.Hardness tester,OM,XRD,SEM were used to investigate the mechanical properties and microstructures of the alloy.The results show that the hardnes...Fe-Cr-Mo-Ni-C-Co alloy was quenched in liquid nitrogen and held for 24 h.Hardness tester,OM,XRD,SEM were used to investigate the mechanical properties and microstructures of the alloy.The results show that the hardness increases by 1-2(HRC)and the compressive strength decreases slightly after cryogenic treatment.The increase in hardness is attributed to the transformation from austenite to martensite and the precipitation of the very tiny carbideη-Fe2C.The decrease in compressive strength is caused by residual stress.The great amount of carbides,such as Cr7C3 and Fe2MoC,in the alloy and the obvious difference in thermal expansion coefficient between these carbides and the matrix at the cryogenic temperatures lead to this residual stress.The microscopy of cryogenic martensite is different from that of the non-cryogenic martensite.The cryogenic martensite is long and fine;while the non-cryogenic martensite is short and coarse.There is obvious surface relief of the cryogenic martensite transformation.It is not orientational of this kind surface relief and the boundary of this surface relief is smooth and in a shape of butterfly.The surface relief in the non-cryogenic martensite is wide and arranged in parallel,and the boundary of surface relief is not smooth.These characteristics may imply different growth ways of the two kinds of martensite.展开更多
The freckle formation and their phase characterization in freckle areas were investigated by means of microstructure analysis approaches and a thermodynamic equilibrium phase calculation method in a Ni-Cr-Mo-Fe-W allo...The freckle formation and their phase characterization in freckle areas were investigated by means of microstructure analysis approaches and a thermodynamic equilibrium phase calculation method in a Ni-Cr-Mo-Fe-W alloy. These results show that in freckle areas a large number of M6C, μ and P phases precipitate in grain boundaries even within grain due to the enrichment and segregation of Mo and C during solidification, which results in small grains in freckle areas. Equilibrium phase and liquid segregation calculation can give an reasonable interpretation of the freckle feature for this alloy.展开更多
基金Project(2012CB825700) supported by the National Basic Research Program of China
文摘Thermal stability,crystallization behavior,Vickers hardness and magnetic properties of the Fe41Co7-xNixCr15Mo14C15B6Y2（x=0,1,3,5） bulk metallic glasses were investigated.The Fe41Co7-xNixCr15Mo14C15B6Y2（x=0,1,3,5） metallic glasses were fabricated by copper mold casting method.The thermal stability and crystallization behavior of the metallic glass rods were investigated by differential scanning calorimetry and isothermal experiments.Hardness measurements for samples annealed at different temperatures for different time were carried out at room temperature by the Vickers hardness tester,and magnetic measurements were performed at different temperatures by the vibrating sample magnetometer.It is shown that the addition of Ni does not play a positive role for enlarging ΔTx and GFA from parameter γ（=Tx/（Tg＋Tl））,and it can,however,increase the activation energy in the initial stage of crystallization by changing the initial crystallization behavior.The minor addition of Ni can refine the crystal grain obtained from the full crystallization experiment.The primary crystallization causes the decrease of hardness in these alloys,and as the crystallization continues,the hardness in all samples increases instead due to the precipitation of carbide and boride.The annealing temperature has an obvious effect on magnetic properties of these alloys,and the minor addition of Ni can effectively prevent the alloy annealed at high temperature to transform from paramagnetic to ferromagnetic state.
文摘Fe-Cr-Mo-Ni-C-Co alloy was quenched in liquid nitrogen and held for 24 h.Hardness tester,OM,XRD,SEM were used to investigate the mechanical properties and microstructures of the alloy.The results show that the hardness increases by 1-2(HRC)and the compressive strength decreases slightly after cryogenic treatment.The increase in hardness is attributed to the transformation from austenite to martensite and the precipitation of the very tiny carbideη-Fe2C.The decrease in compressive strength is caused by residual stress.The great amount of carbides,such as Cr7C3 and Fe2MoC,in the alloy and the obvious difference in thermal expansion coefficient between these carbides and the matrix at the cryogenic temperatures lead to this residual stress.The microscopy of cryogenic martensite is different from that of the non-cryogenic martensite.The cryogenic martensite is long and fine;while the non-cryogenic martensite is short and coarse.There is obvious surface relief of the cryogenic martensite transformation.It is not orientational of this kind surface relief and the boundary of this surface relief is smooth and in a shape of butterfly.The surface relief in the non-cryogenic martensite is wide and arranged in parallel,and the boundary of surface relief is not smooth.These characteristics may imply different growth ways of the two kinds of martensite.
基金supported by the National Natural Science Foundation of China(No.50371006)the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions of MOE,China
文摘The freckle formation and their phase characterization in freckle areas were investigated by means of microstructure analysis approaches and a thermodynamic equilibrium phase calculation method in a Ni-Cr-Mo-Fe-W alloy. These results show that in freckle areas a large number of M6C, μ and P phases precipitate in grain boundaries even within grain due to the enrichment and segregation of Mo and C during solidification, which results in small grains in freckle areas. Equilibrium phase and liquid segregation calculation can give an reasonable interpretation of the freckle feature for this alloy.
