The thirteen mother alloys,C%+1/3Si%=4.45%,differing in their Si,Ce,Sb and Sn contents,were prepared.Seventy grams of these alloys was remelted in a high purity alumina crucible at 1,450oC under an Ar atmosphere,and t...The thirteen mother alloys,C%+1/3Si%=4.45%,differing in their Si,Ce,Sb and Sn contents,were prepared.Seventy grams of these alloys was remelted in a high purity alumina crucible at 1,450oC under an Ar atmosphere,and then cooled at 30 K/min for obtaining their cooling curves.Their graphite morphologies were observed using an optical microscope and an SEM.Their three-dimensional graphite shapes were observed by the SEM using the samples whose matrices were etched off with an acid-aqua solution,to confirm the chunky graphite.For discussing the influence of the Si and Ce contents on the chunky graphite formation,two experiments were carried out.In the first one,the Si contents were changed from 0 to 4% in the 0.15%Ce alloys,and for the second one,the 3.5%Si and 4%Si samples that differed in the Ce contents of 0.1 and 0.2% were used.In the third experiment,the influence of Sb and Sn on the chunky graphite formation was investigated by using the 4%Si and 0.1%Ce samples.The results showed that with the increase of the Si content,the volume fraction of the chunky graphite increases,while the volume fraction of the ledeburite decreases,and the chunky graphite volume fraction in the 0.2%Ce samples is higher than that of the 0.1%Ce samples.The effect of the Sb and Sn additions on the prevention of chunky graphite formation cannot be confirmed due to their high Si contents.Therefore,further studies will be needed in this field.展开更多
In large scale motions of circulations in coastal seas and shallow-water problems, different characteristics of flow in the horizontal plane and in the vertical direction are expected. A new large eddy simulation mode...In large scale motions of circulations in coastal seas and shallow-water problems, different characteristics of flow in the horizontal plane and in the vertical direction are expected. A new large eddy simulation model was proposed. There are some differences between the present method and the other LES models. The philosophy of the large eddy simulation and the directional eddy viscosity method were applied in the horizontal plane and in the vertical direction, respectively. Compared with the other LES models in which there is no difference between horizontal viscosity and vertical viscosity, the proposed method is reasonable.展开更多
文摘The thirteen mother alloys,C%+1/3Si%=4.45%,differing in their Si,Ce,Sb and Sn contents,were prepared.Seventy grams of these alloys was remelted in a high purity alumina crucible at 1,450oC under an Ar atmosphere,and then cooled at 30 K/min for obtaining their cooling curves.Their graphite morphologies were observed using an optical microscope and an SEM.Their three-dimensional graphite shapes were observed by the SEM using the samples whose matrices were etched off with an acid-aqua solution,to confirm the chunky graphite.For discussing the influence of the Si and Ce contents on the chunky graphite formation,two experiments were carried out.In the first one,the Si contents were changed from 0 to 4% in the 0.15%Ce alloys,and for the second one,the 3.5%Si and 4%Si samples that differed in the Ce contents of 0.1 and 0.2% were used.In the third experiment,the influence of Sb and Sn on the chunky graphite formation was investigated by using the 4%Si and 0.1%Ce samples.The results showed that with the increase of the Si content,the volume fraction of the chunky graphite increases,while the volume fraction of the ledeburite decreases,and the chunky graphite volume fraction in the 0.2%Ce samples is higher than that of the 0.1%Ce samples.The effect of the Sb and Sn additions on the prevention of chunky graphite formation cannot be confirmed due to their high Si contents.Therefore,further studies will be needed in this field.
文摘In large scale motions of circulations in coastal seas and shallow-water problems, different characteristics of flow in the horizontal plane and in the vertical direction are expected. A new large eddy simulation model was proposed. There are some differences between the present method and the other LES models. The philosophy of the large eddy simulation and the directional eddy viscosity method were applied in the horizontal plane and in the vertical direction, respectively. Compared with the other LES models in which there is no difference between horizontal viscosity and vertical viscosity, the proposed method is reasonable.
