Fe-Cr-Ni heat resistant alloys with aluminum and silicon addition, alone and in combination, were melted using an intermediate frequency induction furnace with a non-oxidation method. By the oxidation weight gain meth...Fe-Cr-Ni heat resistant alloys with aluminum and silicon addition, alone and in combination, were melted using an intermediate frequency induction furnace with a non-oxidation method. By the oxidation weight gain method, the oxidation resistances of the test alloys were determined at 1,200 ℃ for 500 hours. According to the oxidation weight gains, the oxidation kinetic curves were plotted and the functions were regressed by the least squares method. The results show that the oxidation kinetic curves follow the power function of y = ax^b （a〉0, 0〈b〈1）. The effects of scale compositions on oxidation resistance were studied further by analyses using X-ray diffraction （XRD） and scanning electron microscope （SEM）. It is found that the composite scale compounds of Cr203, a-Al2O3, SiO2 and FeCr2O4, with compact structure and tiny grains, shows complete oxidation resistance at 1,200℃. When the composite scale lacks a-Al2O3 or SiO2, it becomes weak in oxidation resistance with a loose structure. By the criterion of standard Gibbs formation free energy, the model of the nucleation and growth of the composite scale is established. The forming of the composite scale is the result of the competition of being oxidized and reduced between aluminum, silicon and the matrix metal elements of iron, chromium and nickel. The protection of the composite scale is analyzed essentially by electrical conductivity and strength properties.展开更多
The present status of NRIM Creep Data Sheet Project and the recent activities of long-term creep and rupture studies on heat resisting steels are described. The project has been continued to produce long-term data suc...The present status of NRIM Creep Data Sheet Project and the recent activities of long-term creep and rupture studies on heat resisting steels are described. The project has been continued to produce long-term data such as 100 000h-creep rupture strength for 47 kinds of principal heat resisting steels and alloys, including welded joints. The long-term creep deformation behavior and microstructural evolution during creep have been shown to be complicated.展开更多
The standard heat treatment of cast nickel base superalloy K403 is the solid solution treatment of 1210℃/4h, air cooling. It is very difficult to meet the requirements of Aviation Standard HB5155, in which the stre...The standard heat treatment of cast nickel base superalloy K403 is the solid solution treatment of 1210℃/4h, air cooling. It is very difficult to meet the requirements of Aviation Standard HB5155, in which the stress rupture life at 750℃ and 645MPa is longer than 50h. The results showed that the intermediate temperature stress rupture properties impaired by treatment of 1210℃/4h were due to precipitation of too small γ′ phase(<0.2μm) in grains and absence of the secondary carbides at grain boundaries. Microstructure containing the intergranular M6C carbides with envelope of γ′ and the residual coarse γ′ was obtained by means of 1180℃/4h treatment, therefore the stress rupture life was obviously increased to meet the demand of HB5155. The effect of γ′ size was also discussed from the view point of deformation mechanism in this paper.展开更多
Grain structure, dendrite morphologies and shape of MC type carbides ina nickel-base superalloy IN 738 LC are investigated with the addition of carbides,boride, nitride and intermetallic compounds. The results show th...Grain structure, dendrite morphologies and shape of MC type carbides ina nickel-base superalloy IN 738 LC are investigated with the addition of carbides,boride, nitride and intermetallic compounds. The results show that the grain size of theingots can be refined extensively to the order of ASTM M11～12 by combination of anintermetallic compound NixAly, addition together with lowering melt homogeneoustreatment temperature during the melting and casting process. In addition, the processcould restrain the formation of script-type carbides. The new process does not changethe phase constitution, freezing characteristics and sub-structure stability. Therefore, itis considered as an effective and practical method of grain refinement for superalloys.展开更多
Thermal analysis has been adopted to determine the liquidus and eutectic temperature of Fe-20%Cr-Mn alloy over range of Mn and C contents.Using regression analysis,the par- tial quasi-binary phase diagrams of Fe-Mn al...Thermal analysis has been adopted to determine the liquidus and eutectic temperature of Fe-20%Cr-Mn alloy over range of Mn and C contents.Using regression analysis,the par- tial quasi-binary phase diagrams of Fe-Mn alloy(solidification range)have been con- structed.And the effect of Mn content on liquidus and eutectic temperature was discussed.展开更多
In this paper, the composition, two-dimensional and three-dimensional microstructure of heat-resistant wrought aluminum alloy with strong oxidation resistance, heat resistance and easy processing are analyzed by using...In this paper, the composition, two-dimensional and three-dimensional microstructure of heat-resistant wrought aluminum alloy with strong oxidation resistance, heat resistance and easy processing are analyzed by using direct reading spectrometer, metallographic microscope and scanning electron microscope. The main alloy elements of heat-resistant forging aluminum alloy include Cu, Mg, Si, Ni and Fe. The α solid solution of each element in aluminum consists of S phase (Al<sub>2</sub>CuMg), Mg<sub>2</sub>Si phase, bright gray Al<sub>2</sub>CuNi phase and dark brown Al<sub>9</sub>FeNi phase. The distribution of each phase in the aluminum alloy is determined by the three-dimensional energy spectrum analysis of the microstructure, and the distribution of each phase in the crystal position is analyzed. The mechanism of heat resistance, easy processing type and wear resistance is obtained, which provides the theoretical basis for the development and use of heat-resistant forged aluminum alloy.展开更多
The effect of solidification rate on the microstructures of directionallysolidified superalloy DZ22 was studied with the help of a ZMLMC directionalsolidification apparatus which has a superhigh temperature gradient. ...The effect of solidification rate on the microstructures of directionallysolidified superalloy DZ22 was studied with the help of a ZMLMC directionalsolidification apparatus which has a superhigh temperature gradient. The results showthat the size and shapes of Y', (Y+Y') and MC change seriously with the increase in cool-ing rate. When the cooling rate is equal to 54.2K . s-1, Y' particles distnbute evenly;eutectic (Y+Y') in group block and MC in block are distributed in the interdendriticzone.展开更多
The precipitation characteristics and effect on strengthening mechanism of Cu-rich phases during short-time and long-time aging for Super 304H steels with different Cu content were investigated using X-ray diffraction...The precipitation characteristics and effect on strengthening mechanism of Cu-rich phases during short-time and long-time aging for Super 304H steels with different Cu content were investigated using X-ray diffraction （XRD）, scanning electron microscope （SEM） and transmission electron microscope （TEM）. The results show that the size of Cu-rich phase particles increases, the interspace of Cu-rich phase particles decreases and the density of Curich phases increases with the increase of Cu content during short-time aging （approximately 800 h） at 650℃ for Super 304H steels. During long-time aging （more than 2 000 h） at 650 ℃, Cu-rich phase precipitates sufficiently and the strengthening effect of Cu-rich phase is preferable in Super 304H steel containing Cu of 4%. The strengthening effect of Cu-rich phase in Super 304H steels containing Cu of 2.2% or 5% is weaker than that with Cu of 4% during long-time aging （more than 2 000 h）.展开更多
基金supported financially by Komatsu of Japan,grant number31370011370804,in Shandong University,China.
文摘Fe-Cr-Ni heat resistant alloys with aluminum and silicon addition, alone and in combination, were melted using an intermediate frequency induction furnace with a non-oxidation method. By the oxidation weight gain method, the oxidation resistances of the test alloys were determined at 1,200 ℃ for 500 hours. According to the oxidation weight gains, the oxidation kinetic curves were plotted and the functions were regressed by the least squares method. The results show that the oxidation kinetic curves follow the power function of y = ax^b （a〉0, 0〈b〈1）. The effects of scale compositions on oxidation resistance were studied further by analyses using X-ray diffraction （XRD） and scanning electron microscope （SEM）. It is found that the composite scale compounds of Cr203, a-Al2O3, SiO2 and FeCr2O4, with compact structure and tiny grains, shows complete oxidation resistance at 1,200℃. When the composite scale lacks a-Al2O3 or SiO2, it becomes weak in oxidation resistance with a loose structure. By the criterion of standard Gibbs formation free energy, the model of the nucleation and growth of the composite scale is established. The forming of the composite scale is the result of the competition of being oxidized and reduced between aluminum, silicon and the matrix metal elements of iron, chromium and nickel. The protection of the composite scale is analyzed essentially by electrical conductivity and strength properties.
文摘The present status of NRIM Creep Data Sheet Project and the recent activities of long-term creep and rupture studies on heat resisting steels are described. The project has been continued to produce long-term data such as 100 000h-creep rupture strength for 47 kinds of principal heat resisting steels and alloys, including welded joints. The long-term creep deformation behavior and microstructural evolution during creep have been shown to be complicated.
文摘The standard heat treatment of cast nickel base superalloy K403 is the solid solution treatment of 1210℃/4h, air cooling. It is very difficult to meet the requirements of Aviation Standard HB5155, in which the stress rupture life at 750℃ and 645MPa is longer than 50h. The results showed that the intermediate temperature stress rupture properties impaired by treatment of 1210℃/4h were due to precipitation of too small γ′ phase(<0.2μm) in grains and absence of the secondary carbides at grain boundaries. Microstructure containing the intergranular M6C carbides with envelope of γ′ and the residual coarse γ′ was obtained by means of 1180℃/4h treatment, therefore the stress rupture life was obviously increased to meet the demand of HB5155. The effect of γ′ size was also discussed from the view point of deformation mechanism in this paper.
文摘Grain structure, dendrite morphologies and shape of MC type carbides ina nickel-base superalloy IN 738 LC are investigated with the addition of carbides,boride, nitride and intermetallic compounds. The results show that the grain size of theingots can be refined extensively to the order of ASTM M11～12 by combination of anintermetallic compound NixAly, addition together with lowering melt homogeneoustreatment temperature during the melting and casting process. In addition, the processcould restrain the formation of script-type carbides. The new process does not changethe phase constitution, freezing characteristics and sub-structure stability. Therefore, itis considered as an effective and practical method of grain refinement for superalloys.
文摘Thermal analysis has been adopted to determine the liquidus and eutectic temperature of Fe-20%Cr-Mn alloy over range of Mn and C contents.Using regression analysis,the par- tial quasi-binary phase diagrams of Fe-Mn alloy(solidification range)have been con- structed.And the effect of Mn content on liquidus and eutectic temperature was discussed.
文摘In this paper, the composition, two-dimensional and three-dimensional microstructure of heat-resistant wrought aluminum alloy with strong oxidation resistance, heat resistance and easy processing are analyzed by using direct reading spectrometer, metallographic microscope and scanning electron microscope. The main alloy elements of heat-resistant forging aluminum alloy include Cu, Mg, Si, Ni and Fe. The α solid solution of each element in aluminum consists of S phase (Al<sub>2</sub>CuMg), Mg<sub>2</sub>Si phase, bright gray Al<sub>2</sub>CuNi phase and dark brown Al<sub>9</sub>FeNi phase. The distribution of each phase in the aluminum alloy is determined by the three-dimensional energy spectrum analysis of the microstructure, and the distribution of each phase in the crystal position is analyzed. The mechanism of heat resistance, easy processing type and wear resistance is obtained, which provides the theoretical basis for the development and use of heat-resistant forged aluminum alloy.
文摘The effect of solidification rate on the microstructures of directionallysolidified superalloy DZ22 was studied with the help of a ZMLMC directionalsolidification apparatus which has a superhigh temperature gradient. The results showthat the size and shapes of Y', (Y+Y') and MC change seriously with the increase in cool-ing rate. When the cooling rate is equal to 54.2K . s-1, Y' particles distnbute evenly;eutectic (Y+Y') in group block and MC in block are distributed in the interdendriticzone.
基金Sponsored by National Science and Technology Support Plan of China (2007BAE51B02)
文摘The precipitation characteristics and effect on strengthening mechanism of Cu-rich phases during short-time and long-time aging for Super 304H steels with different Cu content were investigated using X-ray diffraction （XRD）, scanning electron microscope （SEM） and transmission electron microscope （TEM）. The results show that the size of Cu-rich phase particles increases, the interspace of Cu-rich phase particles decreases and the density of Curich phases increases with the increase of Cu content during short-time aging （approximately 800 h） at 650℃ for Super 304H steels. During long-time aging （more than 2 000 h） at 650 ℃, Cu-rich phase precipitates sufficiently and the strengthening effect of Cu-rich phase is preferable in Super 304H steel containing Cu of 4%. The strengthening effect of Cu-rich phase in Super 304H steels containing Cu of 2.2% or 5% is weaker than that with Cu of 4% during long-time aging （more than 2 000 h）.
