For the bonding couple of S31042 steel and Ni3Al-based superalloy,joint microstructure regulation plays a pivotal role in improving joint performance.Different pretreatment approaches including solution and cold rolli...For the bonding couple of S31042 steel and Ni3Al-based superalloy,joint microstructure regulation plays a pivotal role in improving joint performance.Different pretreatment approaches including solution and cold rolling treatments were severally applied to the two substrates before vacuum diffusion bonding.Cold rolling treatment in S31042 steel substrate before bonding promoted the coarsening and precipitation behaviors of large amounts of Z(NbCrN)phases during the bonding process so that the AlN phase decreased in the joint area because of the consumption of N atom in the Z phase.And solution treatment for Ni3Al-based superalloy increased the grain boundary mobility and led to the occurrence of dynamic recrystallization in the diffusion area of the joint by reducing segregation and homogenizing the microstructure within the substrate.As a result,the bonded sample with two substrates that are pretreated exhibited a better tensile strength and elongation at 700℃.展开更多
The effect of dendrite arm spacing and the size of γ' phase on stress rupture properties of as-cast Ni3Al-based single crystal superalloy IC6SX was studied.It has been found that the stress rupture properties wer...The effect of dendrite arm spacing and the size of γ' phase on stress rupture properties of as-cast Ni3Al-based single crystal superalloy IC6SX was studied.It has been found that the stress rupture properties were affected by dendrite arm spacing and the size of γ' phase significantly,i.e.,the stress rupture lives of as-cast specimens under the test condition of 1100°C/120 MPa were significantly increased from about 10 h to 31 h with decreasing dendrite arm spacing and the size of γ' phase from 3.0 μm and 1.6 μm to 1.3 μm and 0.8 μm,respectively.The creep cracks generated easily in the brittle Y-NiMo phase.Then the cracks gradually mergered and grew up during creep,and finally led to specimens fracture.The orientated coarsening of γ' phase has been found in the stress ruptured specimens,due to the elements diffusion.However,the γ' phase did not form the integrated structure during the short periods of 10-31 h as the creep tests lasted.展开更多
The Ni3Al-based superalloy was rapidly solidified in the form of droplets with varying diameters.The cooling rate(Rc)is a function of diameter(D)of droplet.With the decrease in droplet sizes(increase in the cooling ra...The Ni3Al-based superalloy was rapidly solidified in the form of droplets with varying diameters.The cooling rate(Rc)is a function of diameter(D)of droplet.With the decrease in droplet sizes(increase in the cooling rates),the volume fraction ofγ’+γeutectic structure increases from 21.31(D=1400 lm,Rc=3.6 9 102 K s-1)to 36.31%(D=270 lm,Rc-=2.3 9 103 K s-1).Moreover,unimodal size distribution of nano-γ’exists in the droplets instead of bimodal dual-size distributions ofγprecipitates that are normal in as-cast alloys.展开更多
As-cast Microstructure of A Designed Polycrystalline Ni3 Al-based Superalloy Is Characterized Using Optical Microscope,scanning Electron Microscope, Transmission Electron Microscope Equipped with Selected Area Diffrac...As-cast Microstructure of A Designed Polycrystalline Ni3 Al-based Superalloy Is Characterized Using Optical Microscope,scanning Electron Microscope, Transmission Electron Microscope Equipped with Selected Area Diffraction System,and the Intermetallic Phase Transformations Involved During Solidification Process Are Determined Based on Thermal Analysis Measurements. the As-cast Microstructure Is Mainly Composed of 80.63 Vol% Dendritic and 19.37 Vol% Interdendritic Phases,and the Dendrite Is Identified As Quasi-cuboidal γ'i Phase Connected by γ-channels Where Ultrafine γ'Ⅱ Particles Are Distributed,and the Interdendritic Phases Are Determined As γ'-γ Eutectic Structure Consisting of Ye Phase with Dotted Quasi-spherical γ'e Particles. During Solidification, the Dendrite Firstly Nucleates from Liquid Melt Near 1348 ℃; Subsequently, the Residual Liquidoid Is Transformed into Interdendritic Phases Around 1326 ℃. Afterward, γ' Phase Will Precipitate from Dendritic Ymatrix with Two-stage Characteristics, Resulting in the Distinct Precipitation of γ'Ⅰ and γ'Ⅱ Phases When Approaching to 1190 And 1043 ℃, Respectively. the Corresponding Transformations Involved During the Solidification Process Can Be Translated As:Liquidoid{Dendrite(γD)(80.63)%→γ'Ⅰ+γ(channel)→γ'Ⅰ+γ'Ⅱ+γ(channel) Residual liquidoid(19.37%)→Interdendrite(γ'E-γE eutectic)}As-cast展开更多
In this work,water cooling,air cooling(AC)and furnace cooling(FC)were applied to investigate the effect of cooling rate on microstructure evolution of primaryγ′in a newly designed Ni3Al-based alloy.The results showe...In this work,water cooling,air cooling(AC)and furnace cooling(FC)were applied to investigate the effect of cooling rate on microstructure evolution of primaryγ′in a newly designed Ni3Al-based alloy.The results showed that nucleation rate of primaryγ′increased with increasing cooling rate.In addition,higher cooling rate shortened growth period of primaryγ′,which made its morphology close to the initial precipitatedγ′.For AC and FC specimens,due to the lower cooling rate,primaryγ′possessed longer growth period and its morphology was mainly due to the evolution of lattice misfit betweenγand primaryγ′.Meanwhile,growth of primaryγ′depended on lattice misfit distribution between its corner and edge area.Moreover,primaryγ′morphologies of sphere,cube and concave cube with tip corners were illustrated by considering interaction between elemental diffusion and elastic strain energy.展开更多
In order to investigate the yielding behavior of the newly developed Ni 3 Al-based intermetallic alloy IC10, yield stresses have been measured in tension and compression with different orientations. The specimens were...In order to investigate the yielding behavior of the newly developed Ni 3 Al-based intermetallic alloy IC10, yield stresses have been measured in tension and compression with different orientations. The specimens were cut from a sheet with different angles inclined from the solidification direction. The inclined angles were taken to be 0 , 22.5 , 45 , 67.5 and 90 . All experiments were conducted at room temperature except for orientation 0 , whose deformation temperatures ranged from 298 to 1273 K. Experimental results show that the yield strength of alloy IC10 has the anomalous behavior which has been observed for other Ll 2 -long-range ordered intermetallic alloys, but it is less pronounced. The abnormalities show the following characteristics: (i) the yield strength increases as the temperature is raised below the peak temperature, (ii) yield strength anisotropy, (iii) tension/compression asymmetry. Compared to Ni 3 Al single crystals, the polycrystalline exhibits some different yielding behaviors which may be due to the high volume fraction of c phase.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52034004 and 52075373).
文摘For the bonding couple of S31042 steel and Ni3Al-based superalloy,joint microstructure regulation plays a pivotal role in improving joint performance.Different pretreatment approaches including solution and cold rolling treatments were severally applied to the two substrates before vacuum diffusion bonding.Cold rolling treatment in S31042 steel substrate before bonding promoted the coarsening and precipitation behaviors of large amounts of Z(NbCrN)phases during the bonding process so that the AlN phase decreased in the joint area because of the consumption of N atom in the Z phase.And solution treatment for Ni3Al-based superalloy increased the grain boundary mobility and led to the occurrence of dynamic recrystallization in the diffusion area of the joint by reducing segregation and homogenizing the microstructure within the substrate.As a result,the bonded sample with two substrates that are pretreated exhibited a better tensile strength and elongation at 700℃.
基金supported by the National Natural Science Foundation of China (Grant No. 50971005)Beihang University Innovation Fund
文摘The effect of dendrite arm spacing and the size of γ' phase on stress rupture properties of as-cast Ni3Al-based single crystal superalloy IC6SX was studied.It has been found that the stress rupture properties were affected by dendrite arm spacing and the size of γ' phase significantly,i.e.,the stress rupture lives of as-cast specimens under the test condition of 1100°C/120 MPa were significantly increased from about 10 h to 31 h with decreasing dendrite arm spacing and the size of γ' phase from 3.0 μm and 1.6 μm to 1.3 μm and 0.8 μm,respectively.The creep cracks generated easily in the brittle Y-NiMo phase.Then the cracks gradually mergered and grew up during creep,and finally led to specimens fracture.The orientated coarsening of γ' phase has been found in the stress ruptured specimens,due to the elements diffusion.However,the γ' phase did not form the integrated structure during the short periods of 10-31 h as the creep tests lasted.
基金supported by the National Natural Science Foundation of China (Nos. 51774212 and 51674175)
文摘The Ni3Al-based superalloy was rapidly solidified in the form of droplets with varying diameters.The cooling rate(Rc)is a function of diameter(D)of droplet.With the decrease in droplet sizes(increase in the cooling rates),the volume fraction ofγ’+γeutectic structure increases from 21.31(D=1400 lm,Rc=3.6 9 102 K s-1)to 36.31%(D=270 lm,Rc-=2.3 9 103 K s-1).Moreover,unimodal size distribution of nano-γ’exists in the droplets instead of bimodal dual-size distributions ofγprecipitates that are normal in as-cast alloys.
基金financially supported by the National Natural Science Foundation of China (Nos.U1660201 and 51474156)the China National Funds for Distinguished Young Scientists (No.51325401)the National High Technology Research and Development Program of China (No.2015AA042504)
文摘As-cast Microstructure of A Designed Polycrystalline Ni3 Al-based Superalloy Is Characterized Using Optical Microscope,scanning Electron Microscope, Transmission Electron Microscope Equipped with Selected Area Diffraction System,and the Intermetallic Phase Transformations Involved During Solidification Process Are Determined Based on Thermal Analysis Measurements. the As-cast Microstructure Is Mainly Composed of 80.63 Vol% Dendritic and 19.37 Vol% Interdendritic Phases,and the Dendrite Is Identified As Quasi-cuboidal γ'i Phase Connected by γ-channels Where Ultrafine γ'Ⅱ Particles Are Distributed,and the Interdendritic Phases Are Determined As γ'-γ Eutectic Structure Consisting of Ye Phase with Dotted Quasi-spherical γ'e Particles. During Solidification, the Dendrite Firstly Nucleates from Liquid Melt Near 1348 ℃; Subsequently, the Residual Liquidoid Is Transformed into Interdendritic Phases Around 1326 ℃. Afterward, γ' Phase Will Precipitate from Dendritic Ymatrix with Two-stage Characteristics, Resulting in the Distinct Precipitation of γ'Ⅰ and γ'Ⅱ Phases When Approaching to 1190 And 1043 ℃, Respectively. the Corresponding Transformations Involved During the Solidification Process Can Be Translated As:Liquidoid{Dendrite(γD)(80.63)%→γ'Ⅰ+γ(channel)→γ'Ⅰ+γ'Ⅱ+γ(channel) Residual liquidoid(19.37%)→Interdendrite(γ'E-γE eutectic)}As-cast
基金financially supported by the Natural Science Foundation of Hebei Province(No.E2019202161)the Highlevel Talent Funding Project of Hebei Province(No.A201902008)+2 种基金the Key R&D Program of Hebei Province(No.19251013D)the College Student Innovation and Entrepreneurship Training Program of Hebei University of Technology(No.S201910080035)the National Key R&D Program of China(No.2018YFB2001805)。
文摘In this work,water cooling,air cooling(AC)and furnace cooling(FC)were applied to investigate the effect of cooling rate on microstructure evolution of primaryγ′in a newly designed Ni3Al-based alloy.The results showed that nucleation rate of primaryγ′increased with increasing cooling rate.In addition,higher cooling rate shortened growth period of primaryγ′,which made its morphology close to the initial precipitatedγ′.For AC and FC specimens,due to the lower cooling rate,primaryγ′possessed longer growth period and its morphology was mainly due to the evolution of lattice misfit betweenγand primaryγ′.Meanwhile,growth of primaryγ′depended on lattice misfit distribution between its corner and edge area.Moreover,primaryγ′morphologies of sphere,cube and concave cube with tip corners were illustrated by considering interaction between elemental diffusion and elastic strain energy.
文摘In order to investigate the yielding behavior of the newly developed Ni 3 Al-based intermetallic alloy IC10, yield stresses have been measured in tension and compression with different orientations. The specimens were cut from a sheet with different angles inclined from the solidification direction. The inclined angles were taken to be 0 , 22.5 , 45 , 67.5 and 90 . All experiments were conducted at room temperature except for orientation 0 , whose deformation temperatures ranged from 298 to 1273 K. Experimental results show that the yield strength of alloy IC10 has the anomalous behavior which has been observed for other Ll 2 -long-range ordered intermetallic alloys, but it is less pronounced. The abnormalities show the following characteristics: (i) the yield strength increases as the temperature is raised below the peak temperature, (ii) yield strength anisotropy, (iii) tension/compression asymmetry. Compared to Ni 3 Al single crystals, the polycrystalline exhibits some different yielding behaviors which may be due to the high volume fraction of c phase.