Isothermal compression tests were used to establish constitutive models of the hot deformation of GH4742 superalloy. The microstructural evolution of double cone samples with large strain gradients during hot deformat...Isothermal compression tests were used to establish constitutive models of the hot deformation of GH4742 superalloy. The microstructural evolution of double cone samples with large strain gradients during hot deformation and subsequent solvus treatment was studied. The results showed that the grain size during dynamic recrystallization (DRX) did not exceed 6 μm, and the volume fraction during DRX did not exceed 45% at all reduction rates when it deformed below the γ′ solvus temperature (1080 ℃). When deformed near the γ′ solvus temperature (1110 ℃), the volume fraction and grain size increase significantly during DRX due to the dissolution and coarsening of some γ′ precipitates. When deformed above the γ′ solvus temperature (1140 ℃), even at a high reduction rate of 20 mm/s, the volume fraction during DRX reached 75%, and the grain size during DRX increased to 25 μm. At a reduction rate of 0.5 mm/s, the grain size during DRX reached 65 μm. When the sample is deformed below the γ′ solvus temperature (1080 ℃), stored strain energy accumulates in the sample, which is beneficial for the development of post dynamic recrystallization during subsequent subsolvus heat treatment, resulting in a noticeable increase in the recrystallization volume fraction. The recrystallization volume fraction of predeformed samples deformed at 1110 and 1140 ℃, followed by subsolvus heat treatment, was almost unchanged. The microstructure of the predeformed sample following supersolvus heat treatment consists of coarse equiaxed grains.展开更多
Enhancing the oxidation resistance of Co-based superalloys by adding a high content of Cr,while simultaneously ensuring the stability of theγ/γ′phases,presents a significant challenge.This study evaluated the alloy...Enhancing the oxidation resistance of Co-based superalloys by adding a high content of Cr,while simultaneously ensuring the stability of theγ/γ′phases,presents a significant challenge.This study evaluated the alloying potential of Co–30Ni–10Al–5V–4Ta using the CALPHAD method,revealing promising characteristics.The developed Co–30Ni–10Al–5V–4Ta–12Cr alloy characterized by high Cr content andγ/γ′two-phase structure,demonstrating highγ′solvus temperature of 1139℃,low density of 8.48 g/cm^(3),minimalγ/γ′lattice misfit of +0.28%,high compressive yield strength of 651 MPa at 800℃,and excellent oxidation resistance with a weight gain of 6.5 mg/cm^(3)after 200 h at 1000℃.Examination of the oxidation behavior at 1000℃ revealed an oxide layer consisting of a porous outer CoO,NiO,and V_(3)O_(4)(CNV)oxide and a denser inner mixed oxide layer comprising CoO,NiO,and V_(3)O_(4)(CNV)oxide,Al_(2)O_(3),Cr_(2)O_(3),CoO,and NiO(CNAC)oxide,and TaO_(2),CoO,and NiO(CNT)oxide.展开更多
Flow behaviors of spray forming low solvus high refractory (LSHR) alloy were investigated using hot compression tests performed on a Gleeble?3500 thermal mechanical simulator at temperatures of 1020?1150 °C and s...Flow behaviors of spray forming low solvus high refractory (LSHR) alloy were investigated using hot compression tests performed on a Gleeble?3500 thermal mechanical simulator at temperatures of 1020?1150 °C and strain rates of 0.0003?1.0 s?1. The constitutive equation was established, power dissipation (η) maps and hot processing maps were plotted. The microstructure evolution and dislocation distribution of domains with different values of η in power dissipation maps were also observed. The results show that the flow stress increases with decreasing temperature and increasing strain rate. The activation energy of the spray forming LSHR alloy is 1243.86 kJ/mol. When the value of η is 0.36 at the strain of 0.5, the domain in the processing map shows characteristics of typical dynamic recrystallization (DRX) and low dislocation density. According to the microstructure evolution and processing maps, the optimum processing condition for good hot workability of spray forming LSHR alloy can be summed up as:temperature range 1110?1150 °C; strain rate range 0.01?0.3 s?1.展开更多
基金supported by the National Science and Technology Major Project of China(2017-VI-0018-0090).
文摘Isothermal compression tests were used to establish constitutive models of the hot deformation of GH4742 superalloy. The microstructural evolution of double cone samples with large strain gradients during hot deformation and subsequent solvus treatment was studied. The results showed that the grain size during dynamic recrystallization (DRX) did not exceed 6 μm, and the volume fraction during DRX did not exceed 45% at all reduction rates when it deformed below the γ′ solvus temperature (1080 ℃). When deformed near the γ′ solvus temperature (1110 ℃), the volume fraction and grain size increase significantly during DRX due to the dissolution and coarsening of some γ′ precipitates. When deformed above the γ′ solvus temperature (1140 ℃), even at a high reduction rate of 20 mm/s, the volume fraction during DRX reached 75%, and the grain size during DRX increased to 25 μm. At a reduction rate of 0.5 mm/s, the grain size during DRX reached 65 μm. When the sample is deformed below the γ′ solvus temperature (1080 ℃), stored strain energy accumulates in the sample, which is beneficial for the development of post dynamic recrystallization during subsequent subsolvus heat treatment, resulting in a noticeable increase in the recrystallization volume fraction. The recrystallization volume fraction of predeformed samples deformed at 1110 and 1140 ℃, followed by subsolvus heat treatment, was almost unchanged. The microstructure of the predeformed sample following supersolvus heat treatment consists of coarse equiaxed grains.
基金supported by the National Natural ScienceFoundation of China(Nos.52371007 and 51831007).
文摘Enhancing the oxidation resistance of Co-based superalloys by adding a high content of Cr,while simultaneously ensuring the stability of theγ/γ′phases,presents a significant challenge.This study evaluated the alloying potential of Co–30Ni–10Al–5V–4Ta using the CALPHAD method,revealing promising characteristics.The developed Co–30Ni–10Al–5V–4Ta–12Cr alloy characterized by high Cr content andγ/γ′two-phase structure,demonstrating highγ′solvus temperature of 1139℃,low density of 8.48 g/cm^(3),minimalγ/γ′lattice misfit of +0.28%,high compressive yield strength of 651 MPa at 800℃,and excellent oxidation resistance with a weight gain of 6.5 mg/cm^(3)after 200 h at 1000℃.Examination of the oxidation behavior at 1000℃ revealed an oxide layer consisting of a porous outer CoO,NiO,and V_(3)O_(4)(CNV)oxide and a denser inner mixed oxide layer comprising CoO,NiO,and V_(3)O_(4)(CNV)oxide,Al_(2)O_(3),Cr_(2)O_(3),CoO,and NiO(CNAC)oxide,and TaO_(2),CoO,and NiO(CNT)oxide.
基金Project(51301143)supported by the National Natural Science Foundation of ChinaProject(2014M560727)supported by the National Postdoctoral Foundation of China+1 种基金Project(2015GZ0228)supported by the Sichuan Province Science-Technology Support Plan,ChinaProject(2682014CX001)supported by the Science and Technology Innovation Project of SWJTU University,China
文摘Flow behaviors of spray forming low solvus high refractory (LSHR) alloy were investigated using hot compression tests performed on a Gleeble?3500 thermal mechanical simulator at temperatures of 1020?1150 °C and strain rates of 0.0003?1.0 s?1. The constitutive equation was established, power dissipation (η) maps and hot processing maps were plotted. The microstructure evolution and dislocation distribution of domains with different values of η in power dissipation maps were also observed. The results show that the flow stress increases with decreasing temperature and increasing strain rate. The activation energy of the spray forming LSHR alloy is 1243.86 kJ/mol. When the value of η is 0.36 at the strain of 0.5, the domain in the processing map shows characteristics of typical dynamic recrystallization (DRX) and low dislocation density. According to the microstructure evolution and processing maps, the optimum processing condition for good hot workability of spray forming LSHR alloy can be summed up as:temperature range 1110?1150 °C; strain rate range 0.01?0.3 s?1.
