The phase and microstructure properties of laser cladding single phase NiAl coating at elevated temperature of 800 °C were investigated by means of XRD,SEM,and HRTEM.It was found that Ni3Al phase with a fine equi...The phase and microstructure properties of laser cladding single phase NiAl coating at elevated temperature of 800 °C were investigated by means of XRD,SEM,and HRTEM.It was found that Ni3Al phase with a fine equiaxial microstructure precipitated along NiAl grain boundaries via the solid-state diffusion of Ni atoms during heating process.NiAl and Ni3Al phases have a common<110>zone axis.The phase and microstructure evolutions of NiAl during heating process can acquire well understand the diffusion behavior of laser cladding NiAl intermetallic compound coating and provide better guidance on its production and practical use.展开更多
The precipitation behavior of Co phases in B2-ordered (Ni,Co)Al has been investigated in terms of transmission electron microscopy. Fine precipitation of fcc-Co occurs in (Ni,Co)Al by aging at temperature over 973K. T...The precipitation behavior of Co phases in B2-ordered (Ni,Co)Al has been investigated in terms of transmission electron microscopy. Fine precipitation of fcc-Co occurs in (Ni,Co)Al by aging at temperature over 973K. The orientation relationship between the fee-Co precipitates and the B2-(Ni,Co)Al matrix follows the Kurdjumow-Sachs (K-S) orientation relation. But when the aging temperature is under 873K the Co precipitates have a hcp crystal structure. The orientation relationship between the hep-Co precipitates and the B2-(Ni,Co)Al matrix follows the Burgers orientation relation. (Ni,Co)Al is hardened appreciably by the fine precipitation of both the fee-Co and hep-Co phases. The temperature dependence of the yield strength of precipitate-containing BS-ordered (Ni, Co)Al was investigated by compression tests over the range of 298-1273K. The fine precipitation of Co phases enhances greatly the low and intermediate temperature yield strength. When the deformation temperature was over 87SK, the strength of precipitate-containing (Ni, Co)Al is comparable to ternary dual-phase (Ni,Co)Al+Ni3Al alloy.展开更多
The effect of coating repair on microstructure and mechanical properties of a directionally solidified nickel base alloy IC6 was studied. The experimental results show that after coating repair treatment, the substrat...The effect of coating repair on microstructure and mechanical properties of a directionally solidified nickel base alloy IC6 was studied. The experimental results show that after coating repair treatment, the substrate/coating interface keeps well, and the combination of coating and substrate is very good, as well as very slight mutual diffusion of alloying elements between substrate and coating occurred. Although coating repair treatment make diffusion time double, only a little amount of Mo diffused into coating, and the elements Cr and Co of NiCoCrAlYHf coating only exist in a thin layer of influence region of the substrate, which has no obvious effect on the microstructure of alloy IC6. Tensile tests at room temperature and stress rupture tests under 1?100?℃, 90?MPa of the coating repaired sample were conducted. The results show that the coating repair has no evident effect on mechanical properties. Therefore, it may be considered that when the coating is unexpectedly destroyed, it can be repaired.展开更多
Progress has been made in intermetallic alloys over the past decade and a half, but intermetallics remain a relatively unexplored class of materials for energy applications. Hence, they offer considerable opportunitie...Progress has been made in intermetallic alloys over the past decade and a half, but intermetallics remain a relatively unexplored class of materials for energy applications. Hence, they offer considerable opportunities both for scientific research on fundamental structural property processing relationships and for technological development. The Department of Energy supports a program of scientific research on intermetallic alloys such as the nickel and iron aluminides and is establishing new research efforts in silicides and Laves phases through the program of the Division of Materials Sciences, of the Office of Basic Energy Sciences. Areas of research include theory and materials simulation, microalloying, high resolution sudies of structure and composition, mechanical properties, point defects and dislocation mechanics, phase transformations, and processing. Research is conducted through programs at the Department of Energy National Laboratories and through grants to academic and industrial researchers.Research results from Division of Materials Sciences programs have provided the basis and transportation. In addition, a cooperative effort between research groups has been established as a project on intermetallic materials under the Center of Excellence in Synthesis and Processing of Advanced Materials.展开更多
The effect of aging at 950?℃ for up to 2?000?h on microstructure and mechanical properties of alloy IC6A was investigated with scanning electron microscopy(SEM), transmission electron microscopy(TEM) and energy dispe...The effect of aging at 950?℃ for up to 2?000?h on microstructure and mechanical properties of alloy IC6A was investigated with scanning electron microscopy(SEM), transmission electron microscopy(TEM) and energy dispersive spectroscopy(EDS) of electron probe micro analyzer(EPMA). The results show that Ni 3Y and Mo 1.24 Ni 0.76 precipitated in the interdendritic area due to the addition of yttrium have no obvious change during high temperature aging. A needle like or rod like phase named Y NiMo precipitated after aging for about 200?h. The amount and size of the Y NiMo phases increase with the increase of aging time, which is similar with that in alloy IC6. The ultimate tensile strength at room temperature and stress rupture life under 1?100?℃, 90?MPa of alloy IC6A have no obvious change before aging for 1?000?h and decrease obviously with increasing aging time after aging for 1000h. The yield strength of alloy IC6A at room temperature decreases obviously after aging for 500h and however, has no obvious change during further aging.展开更多
The microstructures of B2-ordered NiA1 containing α-Fe precipitates have been investigated in terms of transmission electron microscopy. Fine precipitation of α-Fe (bcc structure) occurs in NiA1 by aging around 973...The microstructures of B2-ordered NiA1 containing α-Fe precipitates have been investigated in terms of transmission electron microscopy. Fine precipitation of α-Fe (bcc structure) occurs in NiA1 by aging around 973K. The aging behavior was investigated by microhandness measurements and the temperature dependence of the yield strength of precipitate- comaining B2- ordered NiA1 was investigated by compression tests over the temperature range of 673-1273K. The fine precipitation of α-Fe was found to enhance greatly the low and intermediate temperature yield strength. When the deformation temperature is over 1073K, the strength of precipitate- containing NiA1 was comparable to ternary solid solution hardening NiA1-Fe. Dislocations bypass the particles during deformation and typical Orowan loops were observed surrounding the or-Fe particles after deformation.展开更多
The microstructure and compression behavior at room temperature of a rapidly solidified NiAl-Cr（Mo）-Hf eutectic alloy fabricated by water-cooled copper mold method were studied by a combination of SEM, EDS and compr...The microstructure and compression behavior at room temperature of a rapidly solidified NiAl-Cr（Mo）-Hf eutectic alloy fabricated by water-cooled copper mold method were studied by a combination of SEM, EDS and compressive tests. The rapid solidification results in a shift in the coupled zone for the NiAl-Cr（Mo）-Hf eutectic alloy towards the side of Cr（Mo） phase. So the volume fraction of primary NiAl dendrite is increased which is detrimental to the mechanical behavior. On the other hand, the refined microstructure and fine dispersion Heusler phase by Ni2AlHf are beneficial to the improvement of mechanical properties. As a result, the strength increases by 40% and the compressive ductility increases by two times at room temperature, when compared with those of the as-cast state.展开更多
NiAl alloys offer significant payoffs as structural materials in gas turbine applications due to high melting temperature low density,high thermal conductivity and excellent environmental resistance.Significant improv...NiAl alloys offer significant payoffs as structural materials in gas turbine applications due to high melting temperature low density,high thermal conductivity and excellent environmental resistance.Significant improvements in the material properties and processing have been achieved. The current approach also emphasizes design and test methodologies which can accept a material with limited ductility and damage tolerance. NiAl alloys have been successfully manufactured into a variety of turbine components. A high pressure turbine vane is currently being engine tested.展开更多
NiAl-0.3Ru and NiAl-30Cr-4Mo alloys were fabricated by arc melting method and then annealed at 1 423 K for 12 h. It has been revealed that NiAl-0.3Ru was in a single-phase with large grain size and NiAl-30Cr-4Mo consi...NiAl-0.3Ru and NiAl-30Cr-4Mo alloys were fabricated by arc melting method and then annealed at 1 423 K for 12 h. It has been revealed that NiAl-0.3Ru was in a single-phase with large grain size and NiAl-30Cr-4Mo consisted of multiple eutectic cells. Each cell consisted of alternating plates NiAl and Cr(Mo). The compressive properties including the brittle-ductile transition temperature (BDTT) were tested. NiAl-0.3Ru and NiAl-30Cr-4Mo fractured with a little plastic deformation after yielding below the BDTT, and almost no fracture was found after large deformation up to 60% above the BDTT. Fractograph showed that at the room temperature, the fracture in NiAl-0.3Ru was intergranular and the NiAl-30Cr-4Mo in transgranular along the interface betweenβ-NiAl and Cr (Mo). The compressive properties of NiAl were obviously improved by eutectic alloying with Mo and Cr additions.展开更多
The effect of rotational speed in the friction surfacing of nickel-aluminide reinforced Al-Zn-Mg-Cu alloy matrix composite on commercially pure aluminum was investigated. The nickel-aluminide reinforcement was fabrica...The effect of rotational speed in the friction surfacing of nickel-aluminide reinforced Al-Zn-Mg-Cu alloy matrix composite on commercially pure aluminum was investigated. The nickel-aluminide reinforcement was fabricated by in-situ methods based on adding nickel powders to Al-Zn-Mg-Cu alloy melt during the semi-solid casting process.The findings showed that an increase in the rotational speed from 600 to 1000 r/min raised the coating efficiency from 65% to 76%. Besides, there was no significant difference between coating efficiencies in the coating with and without nickel-aluminide. The outcomes showed that if the coating was applied at a rotational speed of 1000 r/min, a traverse speed of 100 mm/min, and an axial feeding rate of 125 mm/min, the hardness and shear strength of the substrate increased by up to 225% and 195%, respectively. But the wear rate of the substrate dropped by 75%. Although the hardness of the coating containing nickel-aluminide increases by up to 32% compared to the coating without nickel-aluminide, nickel-aluminide does not affect the thermal stability of the coating.展开更多
基金National Natural Science Foundation of China(Grant Nos.50705094,51045004)Innovative Group Foundation from NSFC(Grant No 50421502)National 973 Project(2007 CB607601)
文摘The phase and microstructure properties of laser cladding single phase NiAl coating at elevated temperature of 800 °C were investigated by means of XRD,SEM,and HRTEM.It was found that Ni3Al phase with a fine equiaxial microstructure precipitated along NiAl grain boundaries via the solid-state diffusion of Ni atoms during heating process.NiAl and Ni3Al phases have a common<110>zone axis.The phase and microstructure evolutions of NiAl during heating process can acquire well understand the diffusion behavior of laser cladding NiAl intermetallic compound coating and provide better guidance on its production and practical use.
基金the Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan and the Nationa
文摘The precipitation behavior of Co phases in B2-ordered (Ni,Co)Al has been investigated in terms of transmission electron microscopy. Fine precipitation of fcc-Co occurs in (Ni,Co)Al by aging at temperature over 973K. The orientation relationship between the fee-Co precipitates and the B2-(Ni,Co)Al matrix follows the Kurdjumow-Sachs (K-S) orientation relation. But when the aging temperature is under 873K the Co precipitates have a hcp crystal structure. The orientation relationship between the hep-Co precipitates and the B2-(Ni,Co)Al matrix follows the Burgers orientation relation. (Ni,Co)Al is hardened appreciably by the fine precipitation of both the fee-Co and hep-Co phases. The temperature dependence of the yield strength of precipitate-containing BS-ordered (Ni, Co)Al was investigated by compression tests over the range of 298-1273K. The fine precipitation of Co phases enhances greatly the low and intermediate temperature yield strength. When the deformation temperature was over 87SK, the strength of precipitate-containing (Ni, Co)Al is comparable to ternary dual-phase (Ni,Co)Al+Ni3Al alloy.
文摘The effect of coating repair on microstructure and mechanical properties of a directionally solidified nickel base alloy IC6 was studied. The experimental results show that after coating repair treatment, the substrate/coating interface keeps well, and the combination of coating and substrate is very good, as well as very slight mutual diffusion of alloying elements between substrate and coating occurred. Although coating repair treatment make diffusion time double, only a little amount of Mo diffused into coating, and the elements Cr and Co of NiCoCrAlYHf coating only exist in a thin layer of influence region of the substrate, which has no obvious effect on the microstructure of alloy IC6. Tensile tests at room temperature and stress rupture tests under 1?100?℃, 90?MPa of the coating repaired sample were conducted. The results show that the coating repair has no evident effect on mechanical properties. Therefore, it may be considered that when the coating is unexpectedly destroyed, it can be repaired.
文摘Progress has been made in intermetallic alloys over the past decade and a half, but intermetallics remain a relatively unexplored class of materials for energy applications. Hence, they offer considerable opportunities both for scientific research on fundamental structural property processing relationships and for technological development. The Department of Energy supports a program of scientific research on intermetallic alloys such as the nickel and iron aluminides and is establishing new research efforts in silicides and Laves phases through the program of the Division of Materials Sciences, of the Office of Basic Energy Sciences. Areas of research include theory and materials simulation, microalloying, high resolution sudies of structure and composition, mechanical properties, point defects and dislocation mechanics, phase transformations, and processing. Research is conducted through programs at the Department of Energy National Laboratories and through grants to academic and industrial researchers.Research results from Division of Materials Sciences programs have provided the basis and transportation. In addition, a cooperative effort between research groups has been established as a project on intermetallic materials under the Center of Excellence in Synthesis and Processing of Advanced Materials.
文摘The effect of aging at 950?℃ for up to 2?000?h on microstructure and mechanical properties of alloy IC6A was investigated with scanning electron microscopy(SEM), transmission electron microscopy(TEM) and energy dispersive spectroscopy(EDS) of electron probe micro analyzer(EPMA). The results show that Ni 3Y and Mo 1.24 Ni 0.76 precipitated in the interdendritic area due to the addition of yttrium have no obvious change during high temperature aging. A needle like or rod like phase named Y NiMo precipitated after aging for about 200?h. The amount and size of the Y NiMo phases increase with the increase of aging time, which is similar with that in alloy IC6. The ultimate tensile strength at room temperature and stress rupture life under 1?100?℃, 90?MPa of alloy IC6A have no obvious change before aging for 1?000?h and decrease obviously with increasing aging time after aging for 1000h. The yield strength of alloy IC6A at room temperature decreases obviously after aging for 500h and however, has no obvious change during further aging.
文摘The microstructures of B2-ordered NiA1 containing α-Fe precipitates have been investigated in terms of transmission electron microscopy. Fine precipitation of α-Fe (bcc structure) occurs in NiA1 by aging around 973K. The aging behavior was investigated by microhandness measurements and the temperature dependence of the yield strength of precipitate- comaining B2- ordered NiA1 was investigated by compression tests over the temperature range of 673-1273K. The fine precipitation of α-Fe was found to enhance greatly the low and intermediate temperature yield strength. When the deformation temperature is over 1073K, the strength of precipitate- containing NiA1 was comparable to ternary solid solution hardening NiA1-Fe. Dislocations bypass the particles during deformation and typical Orowan loops were observed surrounding the or-Fe particles after deformation.
文摘The microstructure and compression behavior at room temperature of a rapidly solidified NiAl-Cr（Mo）-Hf eutectic alloy fabricated by water-cooled copper mold method were studied by a combination of SEM, EDS and compressive tests. The rapid solidification results in a shift in the coupled zone for the NiAl-Cr（Mo）-Hf eutectic alloy towards the side of Cr（Mo） phase. So the volume fraction of primary NiAl dendrite is increased which is detrimental to the mechanical behavior. On the other hand, the refined microstructure and fine dispersion Heusler phase by Ni2AlHf are beneficial to the improvement of mechanical properties. As a result, the strength increases by 40% and the compressive ductility increases by two times at room temperature, when compared with those of the as-cast state.
文摘NiAl alloys offer significant payoffs as structural materials in gas turbine applications due to high melting temperature low density,high thermal conductivity and excellent environmental resistance.Significant improvements in the material properties and processing have been achieved. The current approach also emphasizes design and test methodologies which can accept a material with limited ductility and damage tolerance. NiAl alloys have been successfully manufactured into a variety of turbine components. A high pressure turbine vane is currently being engine tested.
基金Project(50571005) supported by the National Natural Science Foundation of China
文摘NiAl-0.3Ru and NiAl-30Cr-4Mo alloys were fabricated by arc melting method and then annealed at 1 423 K for 12 h. It has been revealed that NiAl-0.3Ru was in a single-phase with large grain size and NiAl-30Cr-4Mo consisted of multiple eutectic cells. Each cell consisted of alternating plates NiAl and Cr(Mo). The compressive properties including the brittle-ductile transition temperature (BDTT) were tested. NiAl-0.3Ru and NiAl-30Cr-4Mo fractured with a little plastic deformation after yielding below the BDTT, and almost no fracture was found after large deformation up to 60% above the BDTT. Fractograph showed that at the room temperature, the fracture in NiAl-0.3Ru was intergranular and the NiAl-30Cr-4Mo in transgranular along the interface betweenβ-NiAl and Cr (Mo). The compressive properties of NiAl were obviously improved by eutectic alloying with Mo and Cr additions.
文摘The effect of rotational speed in the friction surfacing of nickel-aluminide reinforced Al-Zn-Mg-Cu alloy matrix composite on commercially pure aluminum was investigated. The nickel-aluminide reinforcement was fabricated by in-situ methods based on adding nickel powders to Al-Zn-Mg-Cu alloy melt during the semi-solid casting process.The findings showed that an increase in the rotational speed from 600 to 1000 r/min raised the coating efficiency from 65% to 76%. Besides, there was no significant difference between coating efficiencies in the coating with and without nickel-aluminide. The outcomes showed that if the coating was applied at a rotational speed of 1000 r/min, a traverse speed of 100 mm/min, and an axial feeding rate of 125 mm/min, the hardness and shear strength of the substrate increased by up to 225% and 195%, respectively. But the wear rate of the substrate dropped by 75%. Although the hardness of the coating containing nickel-aluminide increases by up to 32% compared to the coating without nickel-aluminide, nickel-aluminide does not affect the thermal stability of the coating.
