The oxidation of two two-phase ternary Fe-Cu-Al alloys containing about 5% Al(mole fraction), one Fe-rich and one Cu-rich, were studied at 700℃in 1×105 Pa pure oxygen. The Fe-rich alloy (Fe-15Cu-5Al) shows two q...The oxidation of two two-phase ternary Fe-Cu-Al alloys containing about 5% Al(mole fraction), one Fe-rich and one Cu-rich, were studied at 700℃in 1×105 Pa pure oxygen. The Fe-rich alloy (Fe-15Cu-5Al) shows two quasi-parabolic stages, with a large increase of the parabolic rate constant after about 4 h. The presence of 5% Al does not change greatly the oxidation rate of Fe-15Cu-5Al with respect to a binary Fe-Cu alloy of similar composition, which was quite different from the situation of the same alloys oxidized at 800℃. Oxidation of Fe-15Cu-5Al at 700℃produced an outer layer of iron oxides and an inner layer containing a mixture of copper metal, iron and aluminium oxide. On the contrary, the Cu-rich Fe-85Cu-5Al alloy presents a rather irregular kinetic behavior, with formation of an inner continuous alumina thin layer and a rather irregular outer layer. The outer layer with a rather irregular thickness was mainly composed of a matrix of copper oxides plus some aluminium and iron oxides presenting in the deep part of the layer at certain locations. As a result of the formation of a protective alumina layer, the presence of 5% Al greatly reduced the oxidation rate of Fe-85Cu-5Al with respect to a binary Fe-Cu alloy of similar composition, which was also quite different from the situation of the same alloys oxidized at 800℃. Moreover, the oxidation rate at 700℃of the Fe-85Cu-5Al alloy was much lower than that of Fe-15Cu-5Al alloy due to the same reason..展开更多
The oxidation of two two-phase ternary Fe-Cu-Al alloys containing about 5%(mole fraction) aluminium,one Fe-rich and one Cu-rich, has been studied at 900℃in 1×105 Pa pure oxygen. The Fe-rich Fe-15Cu-5Al alloy pre...The oxidation of two two-phase ternary Fe-Cu-Al alloys containing about 5%(mole fraction) aluminium,one Fe-rich and one Cu-rich, has been studied at 900℃in 1×105 Pa pure oxygen. The Fe-rich Fe-15Cu-5Al alloy presents two quasi-parabolic stages, with a large decrease of the parabolic rate constant after about 50 min. The presence of 5% Al greatly reduces the oxidation rate of this alloy with respect to a binary Fe-Cu alloy of similar composition by forming an external protective Al2O3 layer, which is present near the scale/alloy interface. Due to the high stress-growth effect, this thin Al2O3 layer cannot completely prevent further oxidation of the alloy underneath. On the contrary, the Cu-rich Fe-85Cu-5Al alloy presents a single parabolic stage and forms a thick and porous external scale, coupled to the internal oxidation of Fe and Al. As a result, the oxidation of Cu-rich alloy at 900℃is much faster than that of the Fe-rich alloy.展开更多
The effect of temperature on oxidation behavior of ternary Fe-15Cu-5Al(mole fraction,%) alloy in pure oxygen was studied. Fe-15Cu-5Al alloy presents an irregular high-temperature oxidation behavior between 700-1 000 ...The effect of temperature on oxidation behavior of ternary Fe-15Cu-5Al(mole fraction,%) alloy in pure oxygen was studied. Fe-15Cu-5Al alloy presents an irregular high-temperature oxidation behavior between 700-1 000 ℃,though the kinetic curve at each temperature can be approximately considered as being composed of two quasi-parabolic stages. At 700 ℃ the alloy forms bulky stratified scales. On the contrary,at 800 ℃ the alloy forms an external protective Al2O3 layer. The trend of decrease of oxidation rate does not continue at elevated temperatures. Due to the high stress-growth effect at 900 ℃,the thin Al2O3 layer cannot completely prevent further oxidation of the alloy underneath. When the temperature rises to 1 000 ℃,the high stress-growth effect is more obvious and the alloy forms overgrown large nodules. Compared with the Fe-10Al binary alloy,the presence of 15 % Cu tends to greatly increase the flaw of the formed Al2O3 layer at elevated temperatures,resulting in a peculiar oxidation pattern of Fe-15Cu-5Al alloy.展开更多
The corrosion behavior of ternary Fe-15Cu-5Al(mole fraction,%) alloy was studied at 1 000 ℃ in 0.1 MPa pure oxygen. The Fe-rich alloy shows two parabolic oxidation stages,with a small increase of the parabolic rate c...The corrosion behavior of ternary Fe-15Cu-5Al(mole fraction,%) alloy was studied at 1 000 ℃ in 0.1 MPa pure oxygen. The Fe-rich alloy shows two parabolic oxidation stages,with a small increase of the parabolic rate constant from 1.9×10-9 to 4.1×10-9 g2/(cm4·s). The scale grown on the alloy is very complicated,with formation of overgrown nodules interspersed among bulky stratified scales. The nodules and the bulky stratified scales are always composed of an outer layer of CuFe2O4 and of an inner layer containing Fe2O3 and Fe3O4. Beneath the external scale of the nodules,there is an internal oxidation zone where iron oxide is mixed with copper metal. Furthermore,the base of the internal oxidation zone is characterized by a discontinuous aluminum-enriched layer of either Al2O3 or FeAl2O4. For the stratified scales,no internal oxidation zone is present beneath the innermost Al2O3 or FeAl2O4 layer. Aluminum depletion is present in advance of the internal oxidation front,while iron depletion is not observed. The corrosion feature of the ternary Fe-15Cu-5Al alloy is partly associated with that of the corresponding binary Fe-Cu and Fe-Al alloys. The peculiar scale microstructure observed is considered mainly as a consequence of the limited solubility of the iron and copper components in one another and of the monovariant system of the ternary Fe-15Cu-5Al alloy.展开更多
基金Projects (50071058, 50271079) supported by the National Natural Science Foundation of China Project ([2006]245) supported by Science and Technology Research Item of Jiangxi Provincial Department of Education
文摘The oxidation of two two-phase ternary Fe-Cu-Al alloys containing about 5% Al(mole fraction), one Fe-rich and one Cu-rich, were studied at 700℃in 1×105 Pa pure oxygen. The Fe-rich alloy (Fe-15Cu-5Al) shows two quasi-parabolic stages, with a large increase of the parabolic rate constant after about 4 h. The presence of 5% Al does not change greatly the oxidation rate of Fe-15Cu-5Al with respect to a binary Fe-Cu alloy of similar composition, which was quite different from the situation of the same alloys oxidized at 800℃. Oxidation of Fe-15Cu-5Al at 700℃produced an outer layer of iron oxides and an inner layer containing a mixture of copper metal, iron and aluminium oxide. On the contrary, the Cu-rich Fe-85Cu-5Al alloy presents a rather irregular kinetic behavior, with formation of an inner continuous alumina thin layer and a rather irregular outer layer. The outer layer with a rather irregular thickness was mainly composed of a matrix of copper oxides plus some aluminium and iron oxides presenting in the deep part of the layer at certain locations. As a result of the formation of a protective alumina layer, the presence of 5% Al greatly reduced the oxidation rate of Fe-85Cu-5Al with respect to a binary Fe-Cu alloy of similar composition, which was also quite different from the situation of the same alloys oxidized at 800℃. Moreover, the oxidation rate at 700℃of the Fe-85Cu-5Al alloy was much lower than that of Fe-15Cu-5Al alloy due to the same reason..
基金Project(KF0610) supported by the Open Project Program of Key Laboratory of Low Dimensional Materials and Application Technology (Xiangtan University), Ministry of Education, ChinaProject ([2006]245) supported by Science and Technology Research Item of Jiangxi Provincial Department of Education, China
文摘The oxidation of two two-phase ternary Fe-Cu-Al alloys containing about 5%(mole fraction) aluminium,one Fe-rich and one Cu-rich, has been studied at 900℃in 1×105 Pa pure oxygen. The Fe-rich Fe-15Cu-5Al alloy presents two quasi-parabolic stages, with a large decrease of the parabolic rate constant after about 50 min. The presence of 5% Al greatly reduces the oxidation rate of this alloy with respect to a binary Fe-Cu alloy of similar composition by forming an external protective Al2O3 layer, which is present near the scale/alloy interface. Due to the high stress-growth effect, this thin Al2O3 layer cannot completely prevent further oxidation of the alloy underneath. On the contrary, the Cu-rich Fe-85Cu-5Al alloy presents a single parabolic stage and forms a thick and porous external scale, coupled to the internal oxidation of Fe and Al. As a result, the oxidation of Cu-rich alloy at 900℃is much faster than that of the Fe-rich alloy.
基金Project ([2005]224) supported by Science and Technology Research Item of Jiangxi Provincial Department of Science and Technology
文摘The effect of temperature on oxidation behavior of ternary Fe-15Cu-5Al(mole fraction,%) alloy in pure oxygen was studied. Fe-15Cu-5Al alloy presents an irregular high-temperature oxidation behavior between 700-1 000 ℃,though the kinetic curve at each temperature can be approximately considered as being composed of two quasi-parabolic stages. At 700 ℃ the alloy forms bulky stratified scales. On the contrary,at 800 ℃ the alloy forms an external protective Al2O3 layer. The trend of decrease of oxidation rate does not continue at elevated temperatures. Due to the high stress-growth effect at 900 ℃,the thin Al2O3 layer cannot completely prevent further oxidation of the alloy underneath. When the temperature rises to 1 000 ℃,the high stress-growth effect is more obvious and the alloy forms overgrown large nodules. Compared with the Fe-10Al binary alloy,the presence of 15 % Cu tends to greatly increase the flaw of the formed Al2O3 layer at elevated temperatures,resulting in a peculiar oxidation pattern of Fe-15Cu-5Al alloy.
基金Project (05111) supported by the Open Project Program of Key Laboratory of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, ChinaProject ([2005]224) supported by the Science and Technology Research Item of Jiangxi Provincial Department of Science and Technology, China
文摘The corrosion behavior of ternary Fe-15Cu-5Al(mole fraction,%) alloy was studied at 1 000 ℃ in 0.1 MPa pure oxygen. The Fe-rich alloy shows two parabolic oxidation stages,with a small increase of the parabolic rate constant from 1.9×10-9 to 4.1×10-9 g2/(cm4·s). The scale grown on the alloy is very complicated,with formation of overgrown nodules interspersed among bulky stratified scales. The nodules and the bulky stratified scales are always composed of an outer layer of CuFe2O4 and of an inner layer containing Fe2O3 and Fe3O4. Beneath the external scale of the nodules,there is an internal oxidation zone where iron oxide is mixed with copper metal. Furthermore,the base of the internal oxidation zone is characterized by a discontinuous aluminum-enriched layer of either Al2O3 or FeAl2O4. For the stratified scales,no internal oxidation zone is present beneath the innermost Al2O3 or FeAl2O4 layer. Aluminum depletion is present in advance of the internal oxidation front,while iron depletion is not observed. The corrosion feature of the ternary Fe-15Cu-5Al alloy is partly associated with that of the corresponding binary Fe-Cu and Fe-Al alloys. The peculiar scale microstructure observed is considered mainly as a consequence of the limited solubility of the iron and copper components in one another and of the monovariant system of the ternary Fe-15Cu-5Al alloy.
