1873K时镁对钢中氧化物、硫化物的共同变质机理

探讨了1873 K时不同氧硫条件下镁对钢中夹杂物变质的影响.在本实验条件下,Mg在钢液中优先变质氧化物夹杂,随后变质硫化物夹杂,低硫实验钢中镁脱氧产物转变顺序为Al₂O₃→MgAl₂O₄→Mg-Al-O-S.镁合金加入1或5min,就可实现氧化物的完全变质,但硫化物的变质则要缓慢的多.当高硫实验钢中元素含量满足一定条件时,镁可以将氧化物、硫化物同时变质成为复合氧硫夹杂物,夹杂物按照Al₂O₃→MgO→MgO+MgAl₂O₄+MgS转变,但由于其变质产生的MgO-MgAl₂O₄产物层阻碍了变质反应的进一步发生.这种夹杂物可以起到固定硫的作用,同时有效控制夹杂物直径的增大.     

The dissolution behaviour of titanium oxide phases in synthetic Bayer liquors at 90 °C

Many of the bauxites currently being processed to alumina contain titanium minerals, yet little fundamental knowledge is available regarding their dissolution behaviour in Bayer liquors. In this paper the dissolution of various titanium oxide phases (anatase, rutile, sodium titanate and calcium titanate) are presented. It is shown that rutile, calcium titanate and sodium titanate have the expected dissolution behaviour, which increases with free caustic concentration. Anatase, too, generally increases in dissolution with free caustic concentration. However, anatase is shown to have an anomalous behaviour when gibbsite co-precipitates. In this case, the dissolution of anatase does not follow the expected free caustic trend. According to the data presented, the most probable cause is an impervious aluminium/sodium titanate surface layer hindering further dissolution.     

Experiments on Flow at a 90° Open-Channel Junction

Although open-channel junctions are common in many hydraulic structures, no comprehensive data set has been compiled that describes the 3D flow field within the junction itself. This physical model study examined a 90°, sharp-edged, open-channel junction for channels of equal width. Depth measurements were made using a point gauge while velocity measurements were taken using an acoustic doppler velocimeter over a grid defined throughout the junction region. The average velocity and turbulence intensity were calculated from a time series of velocities that was recorded at each location. In addition, a 2D mapping of the water surface was performed on a 76.2 mm square grid throughout the channel junction. This paper presents the details of the experimental procedure and the general flow characteristics observed. The full data set generated during this experimental work is available for downloading on the Internet. Using a small portion of the data recorded, an evaluation of several previously proposed theories of combining flow in open-channel junctions is presented. This has revealed that the simplified mathematical model gives reasonable prediction of the experimental results. The complete data set describing combining flows at a 90° open-channel junction is presented as a resource for the validation of 3D computational fluid dynamics codes that utilize a free-surface model.     

Phase transformations in a binary 10 at % Si-90 at % Al alloy at high pressures and temperatures

Differential barothermal analysis of the phase transformations in a 10 at % Si-90 at % Al alloy has been performed at temperatures up to 700°C in an argon atmosphere compressed to 100 MPa. A slight change of the eutectic melting/solidification temperature is found. The liquidus temperature of the alloy, which is determined upon melting and solidification, coincides with that determined at atmospheric pressure. At 551–554°C, an aluminum-based solid solution decomposes with the formation of silicon nanoprecipitates. The porosity of the alloy after barothermal analysis is almost unchanged. The lattice parameters of micron-sized silicon particles decrease, whereas those of nanoparticles increase relative to the tabulated parameters. The lattice parameters of aluminum subjected to solidification and cooling in a compressed argon medium decreases. The micorhardness of the aluminum matrix of the alloy corresponds to that of pure aluminum.