The role of double oxide film （bifilm） defects in the formation of gas porosity in commercial purity and Srcontaining AI alloys was investigated by means of a reduced pressure test （RPT） technique. The liquid meta...The role of double oxide film （bifilm） defects in the formation of gas porosity in commercial purity and Srcontaining AI alloys was investigated by means of a reduced pressure test （RPT） technique. The liquid metal was poured from a height into a crucible to introduce oxide defects into the melt. The melt was then subjected to different ＂hydrogen addition＂ and ＂holding in liquid state＂ regimes before RPT samples were taken. The RPT samples were then characterized by determining their porosity parameters and examining the internal surfaces of the pores formed in them by scanning electron microscopy. The results indicated oxide defects as the initiation sites for the growth of gas porosity, both in commercial purity and Sr-containing AI alloys. The results also rejected reduction of the surface tension of the melt, increase in the volumetric shrinkage and reduction in interdendritic feeding as the possible causes of an increase in the porosity content of the AI castings modified with strontium. The change in the composition of the oxide layers of double oxide film defects was suggested to be responsible for this behaviour.展开更多
The morphology of double oxide film defects and their influence on the tensile mechanical properties of a commercial Cu-Al （C95800） alloy were investigated in this study. Plane castings were produced with two types ...The morphology of double oxide film defects and their influence on the tensile mechanical properties of a commercial Cu-Al （C95800） alloy were investigated in this study. Plane castings were produced with two types of pouting systems, and their tensile properties were measured and then analyzed by means of Weibull statistics method. The fracture surfaces of the tensile specimens were examined using scanning electron microscopy equipped with energy-dispersive spectroscopy. A large amount of double oxide film defects were observed on the tensile fractured specimens of the topfilled plane castings, and their chemical composition is identified to be Al2O3. Weibull statistics analyses showed that the double oxide film defects significantly reduce mechanical properties of the castings investigated. Furthermore, the ultimate tensile strength is more obviously deteriorated by double oxide film defects than elongation.展开更多
文摘The role of double oxide film （bifilm） defects in the formation of gas porosity in commercial purity and Srcontaining AI alloys was investigated by means of a reduced pressure test （RPT） technique. The liquid metal was poured from a height into a crucible to introduce oxide defects into the melt. The melt was then subjected to different ＂hydrogen addition＂ and ＂holding in liquid state＂ regimes before RPT samples were taken. The RPT samples were then characterized by determining their porosity parameters and examining the internal surfaces of the pores formed in them by scanning electron microscopy. The results indicated oxide defects as the initiation sites for the growth of gas porosity, both in commercial purity and Sr-containing AI alloys. The results also rejected reduction of the surface tension of the melt, increase in the volumetric shrinkage and reduction in interdendritic feeding as the possible causes of an increase in the porosity content of the AI castings modified with strontium. The change in the composition of the oxide layers of double oxide film defects was suggested to be responsible for this behaviour.
文摘The morphology of double oxide film defects and their influence on the tensile mechanical properties of a commercial Cu-Al （C95800） alloy were investigated in this study. Plane castings were produced with two types of pouting systems, and their tensile properties were measured and then analyzed by means of Weibull statistics method. The fracture surfaces of the tensile specimens were examined using scanning electron microscopy equipped with energy-dispersive spectroscopy. A large amount of double oxide film defects were observed on the tensile fractured specimens of the topfilled plane castings, and their chemical composition is identified to be Al2O3. Weibull statistics analyses showed that the double oxide film defects significantly reduce mechanical properties of the castings investigated. Furthermore, the ultimate tensile strength is more obviously deteriorated by double oxide film defects than elongation.
