The cormsion in air of a two-phase Cu-75Cr alloy was studied at 700-900℃. Thealloy cormded nearly parabolically at 700-800℃, but at 900℃ its instantaneousparabolic mte constant decreased with time. The scales were ...The cormsion in air of a two-phase Cu-75Cr alloy was studied at 700-900℃. Thealloy cormded nearly parabolically at 700-800℃, but at 900℃ its instantaneousparabolic mte constant decreased with time. The scales were complex and consistedof an outermost layer of copper oxide generally followed bg a layer of the double ox-ide Cu2 Cr2 O4 sometimes containing particles of unoxidized chromium surmunded bya chromia layer. An innermost layer of chromia was also observed in some cases.Finally metallic copper was al8o frequently mixed with chromia particles. No Cr de-pletion was observed in the alloy close to the inteffoce with the scale. In any case,this alloy was not able to form an exclusive continuous protective chromia layer. Thespecial cormsion behavior Of this alloy is typical of two-phase binary systems with alange solubility gaP in which the outwaof dthesion fiux of the most-reactive componentin the alloy is strongly reduced and may be inswncient to fOrm a protective externallayer of the cormsponding oxide. In paTticular, the presence of particles of Cr withina double oxide layer is very unusual and is allowed only for the kinetic reason.展开更多
This paper presents an analysis of the conditions of stability of the different forms of internal oxidation of ideal ternary A-B-C alloys,where A is the most noble and C the most reactive component, forming insoluble ...This paper presents an analysis of the conditions of stability of the different forms of internal oxidation of ideal ternary A-B-C alloys,where A is the most noble and C the most reactive component, forming insoluble oxide and exposed to high pressures of a single oxidant.The treatment,based on an extension to ternary alloys of Wagner' s criterion for the transition from internal to external oxidation in binary alloys,allows to predict the existence of three different forms of internal oxidation.In fact,in addition to the most common kinds of internal attack,involving the coupled internal oxidation of B+C beneath external AO scales and the internal oxidation of C beneath external BO scales,a third mode, involving the internal oxidation of C beneath external scales composed of mixtures of AO+BO,becomes also possible under special conditions.A combination of the boundary conditions for the existence of these different types of internal oxidation allows to predict three different kinds of complete maps for the internal oxidation in these systems,one of which involves only two modes,while the other two involve all the three possible modes of internal oxidation.展开更多
文摘The cormsion in air of a two-phase Cu-75Cr alloy was studied at 700-900℃. Thealloy cormded nearly parabolically at 700-800℃, but at 900℃ its instantaneousparabolic mte constant decreased with time. The scales were complex and consistedof an outermost layer of copper oxide generally followed bg a layer of the double ox-ide Cu2 Cr2 O4 sometimes containing particles of unoxidized chromium surmunded bya chromia layer. An innermost layer of chromia was also observed in some cases.Finally metallic copper was al8o frequently mixed with chromia particles. No Cr de-pletion was observed in the alloy close to the inteffoce with the scale. In any case,this alloy was not able to form an exclusive continuous protective chromia layer. Thespecial cormsion behavior Of this alloy is typical of two-phase binary systems with alange solubility gaP in which the outwaof dthesion fiux of the most-reactive componentin the alloy is strongly reduced and may be inswncient to fOrm a protective externallayer of the cormsponding oxide. In paTticular, the presence of particles of Cr withina double oxide layer is very unusual and is allowed only for the kinetic reason.
基金supports by the National Natural Science Foundation of China(NSFC) under the research grants No.50571107 & 50671114
文摘This paper presents an analysis of the conditions of stability of the different forms of internal oxidation of ideal ternary A-B-C alloys,where A is the most noble and C the most reactive component, forming insoluble oxide and exposed to high pressures of a single oxidant.The treatment,based on an extension to ternary alloys of Wagner' s criterion for the transition from internal to external oxidation in binary alloys,allows to predict the existence of three different forms of internal oxidation.In fact,in addition to the most common kinds of internal attack,involving the coupled internal oxidation of B+C beneath external AO scales and the internal oxidation of C beneath external BO scales,a third mode, involving the internal oxidation of C beneath external scales composed of mixtures of AO+BO,becomes also possible under special conditions.A combination of the boundary conditions for the existence of these different types of internal oxidation allows to predict three different kinds of complete maps for the internal oxidation in these systems,one of which involves only two modes,while the other two involve all the three possible modes of internal oxidation.
