Environmental embrittlement in A3B-type intermetallics based on Ni3Al and Fe3Al has been studied in this paper. For the Ni3Al doped with 120 wt ppm B and Ni,(Al,Cr.Zr) doped with 80 wt ppm B,their elongation and ultim...Environmental embrittlement in A3B-type intermetallics based on Ni3Al and Fe3Al has been studied in this paper. For the Ni3Al doped with 120 wt ppm B and Ni,(Al,Cr.Zr) doped with 80 wt ppm B,their elongation and ultimate tensile strength decreased in the sequence:of vacuum > air >hydrogen. while for Ni,(Al,Mn) doped with 400 wt ppm B no envifonmental degradation was ob served, although a -Ni3(Al,Mn) alloy without B showed a decrease in ductility when tested in air in stead of oxygen. It is supposed that boron and hydrogen compete for the occupation of interstitial sites near grain boundaries. If boron content is sufficiently low, hydrogen embrittlement occurs ;however, if its content is sufficiently high. boron addition is capable of eliminating envjronmental ef fect in Ni3Al-based alloysi As to the micromechanism of hydrogen embrittlement in Ni3Al+B. S EM in situ observations showed that both grain boundary decohesion and a high stress concentration con tributed to hydrogen-assisted jntergranu lar cracking in this alloy. For the Fe3Al and Fe3 (Al.Cr) alloys.their mechanical properties depended strongly on grain size / grain shape and testing environment. A strain rate effect on ductiIity and fracture strength was also observed in the Fe3Al and Fe,(Al,Cr)+B aIloys. Preoxidation increased the ductility of the Fe,(Al,Cr)+B alloy. All these results can be rationalized from a hypothesis that surface reaction is the controlling process in embrittling Fe3Al-based alloys.展开更多
A comprehensive review of low temperature environmental embrittlement in intermetallics is pres- ented. Moisture and hydrogen are shown to severely embrittle many intermetallics, including iron, nickel and titanium al...A comprehensive review of low temperature environmental embrittlement in intermetallics is pres- ented. Moisture and hydrogen are shown to severely embrittle many intermetallics, including iron, nickel and titanium aluminides. The roles of composition, microstructure and external test variables are emphasized. Several methods to reduce or avoid embrittlement are described.展开更多
The room temperature tensile properties of cold rolled and annealed Fe 3(Al,Cr,Zr) alloy are similar to those of warm rolled Fe 3Al alloys. The cold rolled Fe 3(Al,Cr,Zr) alloy is also susceptible to test enviro...The room temperature tensile properties of cold rolled and annealed Fe 3(Al,Cr,Zr) alloy are similar to those of warm rolled Fe 3Al alloys. The cold rolled Fe 3(Al,Cr,Zr) alloy is also susceptible to test environments. It has been shown that the ductility in various environments decreases in sequence of oxygen—oil—air—distilled water. The results of X ray diffraction analysis show that (211) preferred orientation of B 2 phase appears in cold rolled Fe 3(Al,Cr,Zr) alloy after recrystallization annealing.展开更多
The effect of boron doping on the sensitivity to environmental embrittlement of Ni3Al-based alloys was investigated in this paper. The results show that the ductilizing effect of boron in Ni3Al is partly to suppress ...The effect of boron doping on the sensitivity to environmental embrittlement of Ni3Al-based alloys was investigated in this paper. The results show that the ductilizing effect of boron in Ni3Al is partly to suppress moisture-induced hydrogen embrittlement.The mechanism of this suppressing effect of boron relates to its severely decreasing the hydrogen diffusivity by boron segregated at the grain boundaries. The surface reaction of Fe3Al with water vapor and oxygen was experimentally confirmed by AES and XPS analysis. The kinetics of these reactions can be used to explain the different ductility behavior of aluminides in various environments.展开更多
Considering the intrinsic and environmental embrittlement(IE and EE).the room temperature embrittlement of Fe_3Al and FeAl is analysed by means of empirical electron theory of solids and molecules.It is found that bot...Considering the intrinsic and environmental embrittlement(IE and EE).the room temperature embrittlement of Fe_3Al and FeAl is analysed by means of empirical electron theory of solids and molecules.It is found that both IE and EE exist in Fe_3Al and FeAl.The IE is determined by the characteristic of bond structure and electron distribution;and the EE results from the remarkable decrease of local metallicity and the formation of severe anisotropy bonds when the interstitial sites have been occupied by solute hydrogen.On the basis of analysis results,the effective methods are proposed to improve the ductilities in Fe_3Al and FeAl.展开更多
The study examines the friction and wear properties of Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloys under varying gas conditions.The alloy was tested in the presence of oxygen and carbon dioxide using a controlled atmosphere w...The study examines the friction and wear properties of Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloys under varying gas conditions.The alloy was tested in the presence of oxygen and carbon dioxide using a controlled atmosphere wear tester.The study revealed that the wear environ‐mental embrittlement resulted from the diffusion of reactive atomic hydrogen into the interior of the Ni_(3)Al-Ni_(3)V alloy.The addition of Zr elements decreased the proportion of Al elements on the surface of the Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloy and reduced the proportion of H atoms produced by the chemical reaction between atmospheric water vapour and Al elements.This inhibited the environmental embrittlement and improved the performance of the Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloy.The wear performance of Ni_(5)Zr alloy is superior to that of Ni_(3)Al-Ni_(3)V.When exposed to air in an air environment,the surface of Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloy forms a protective Al_(2)O_(3) oxide film on the workpiece,result‐ing in a reduction of the friction coefficient and wear rate of the alloy.The wear mechanism of the alloy is mainly oxidation wear and abra‐sive wear.In an oxygen environment,the surface of the alloy generates a significant amount of Al_(2)O_(3) oxide film.The flaking of the oxide film leads to an increase in the friction coefficient and wear rate of the alloy.In a carbon dioxide environment,the surface of the alloy un‐dergoes severe deformation,and plough lines become apparent.This is accompanied by flaking Si_(3)N_(4) abrasive chips adhering to the sur‐face of the alloy,which intensifies the wear of the alloy.The primary wear mechanism is abrasive wear.Therefore,the friction coefficient and wear rate of the Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloy in the atmosphere are optimal.展开更多
文摘Environmental embrittlement in A3B-type intermetallics based on Ni3Al and Fe3Al has been studied in this paper. For the Ni3Al doped with 120 wt ppm B and Ni,(Al,Cr.Zr) doped with 80 wt ppm B,their elongation and ultimate tensile strength decreased in the sequence:of vacuum > air >hydrogen. while for Ni,(Al,Mn) doped with 400 wt ppm B no envifonmental degradation was ob served, although a -Ni3(Al,Mn) alloy without B showed a decrease in ductility when tested in air in stead of oxygen. It is supposed that boron and hydrogen compete for the occupation of interstitial sites near grain boundaries. If boron content is sufficiently low, hydrogen embrittlement occurs ;however, if its content is sufficiently high. boron addition is capable of eliminating envjronmental ef fect in Ni3Al-based alloysi As to the micromechanism of hydrogen embrittlement in Ni3Al+B. S EM in situ observations showed that both grain boundary decohesion and a high stress concentration con tributed to hydrogen-assisted jntergranu lar cracking in this alloy. For the Fe3Al and Fe3 (Al.Cr) alloys.their mechanical properties depended strongly on grain size / grain shape and testing environment. A strain rate effect on ductiIity and fracture strength was also observed in the Fe3Al and Fe,(Al,Cr)+B aIloys. Preoxidation increased the ductility of the Fe,(Al,Cr)+B alloy. All these results can be rationalized from a hypothesis that surface reaction is the controlling process in embrittling Fe3Al-based alloys.
文摘A comprehensive review of low temperature environmental embrittlement in intermetallics is pres- ented. Moisture and hydrogen are shown to severely embrittle many intermetallics, including iron, nickel and titanium aluminides. The roles of composition, microstructure and external test variables are emphasized. Several methods to reduce or avoid embrittlement are described.
文摘The room temperature tensile properties of cold rolled and annealed Fe 3(Al,Cr,Zr) alloy are similar to those of warm rolled Fe 3Al alloys. The cold rolled Fe 3(Al,Cr,Zr) alloy is also susceptible to test environments. It has been shown that the ductility in various environments decreases in sequence of oxygen—oil—air—distilled water. The results of X ray diffraction analysis show that (211) preferred orientation of B 2 phase appears in cold rolled Fe 3(Al,Cr,Zr) alloy after recrystallization annealing.
文摘The effect of boron doping on the sensitivity to environmental embrittlement of Ni3Al-based alloys was investigated in this paper. The results show that the ductilizing effect of boron in Ni3Al is partly to suppress moisture-induced hydrogen embrittlement.The mechanism of this suppressing effect of boron relates to its severely decreasing the hydrogen diffusivity by boron segregated at the grain boundaries. The surface reaction of Fe3Al with water vapor and oxygen was experimentally confirmed by AES and XPS analysis. The kinetics of these reactions can be used to explain the different ductility behavior of aluminides in various environments.
文摘Considering the intrinsic and environmental embrittlement(IE and EE).the room temperature embrittlement of Fe_3Al and FeAl is analysed by means of empirical electron theory of solids and molecules.It is found that both IE and EE exist in Fe_3Al and FeAl.The IE is determined by the characteristic of bond structure and electron distribution;and the EE results from the remarkable decrease of local metallicity and the formation of severe anisotropy bonds when the interstitial sites have been occupied by solute hydrogen.On the basis of analysis results,the effective methods are proposed to improve the ductilities in Fe_3Al and FeAl.
基金Supported by the Natural Science Foundation of Hunan Province of China (2020JJ4312)。
文摘The study examines the friction and wear properties of Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloys under varying gas conditions.The alloy was tested in the presence of oxygen and carbon dioxide using a controlled atmosphere wear tester.The study revealed that the wear environ‐mental embrittlement resulted from the diffusion of reactive atomic hydrogen into the interior of the Ni_(3)Al-Ni_(3)V alloy.The addition of Zr elements decreased the proportion of Al elements on the surface of the Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloy and reduced the proportion of H atoms produced by the chemical reaction between atmospheric water vapour and Al elements.This inhibited the environmental embrittlement and improved the performance of the Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloy.The wear performance of Ni_(5)Zr alloy is superior to that of Ni_(3)Al-Ni_(3)V.When exposed to air in an air environment,the surface of Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloy forms a protective Al_(2)O_(3) oxide film on the workpiece,result‐ing in a reduction of the friction coefficient and wear rate of the alloy.The wear mechanism of the alloy is mainly oxidation wear and abra‐sive wear.In an oxygen environment,the surface of the alloy generates a significant amount of Al_(2)O_(3) oxide film.The flaking of the oxide film leads to an increase in the friction coefficient and wear rate of the alloy.In a carbon dioxide environment,the surface of the alloy un‐dergoes severe deformation,and plough lines become apparent.This is accompanied by flaking Si_(3)N_(4) abrasive chips adhering to the sur‐face of the alloy,which intensifies the wear of the alloy.The primary wear mechanism is abrasive wear.Therefore,the friction coefficient and wear rate of the Ni_(3)Al-Ni_(3)V-Zr-Ni_(5)Zr alloy in the atmosphere are optimal.
