An assessment of the Fe-O-Si system

The thermodynamic properties of the Fe-O-Si system have been studied with particular emphasis on the slag system FeO-Fe₂O₃-SiO₂. The liquid phase is described using an ionic two-sublattice model, while fayalite is treated as a stoichiometric phase. The available experimental data were critically examined and a self-consistent set of data was chosen to be used in the assessment, which was carried out taking into account higher order information from the Ca-Fe-O-Si system.     

An assessment of the CaO-SiO2 system

An evaluation of the CaO-SiO₂ system has been made using a newly developed model, a two-sublattice model for ionic solutions. Two alternatives were tested. In the first one, three anions were assumed, O⁻², SiO₄ ⁻⁴, and SiO₃ ⁻². In the second one, SiO₃ ⁻² was omitted. A set of parameter values describing the Gibbs energy of the liquid phase and solid phases was fixed for each alternative by a computer-operated optimization procedure called PARROT. Satisfactory assessments were achieved over the whole phase diagram range with both alternatives. The main difference between them occurs at the monotectic point. A comparison between calculated properties and experimental data is given. Formerly Research Associate, Royal Institute of Technoloy     

Dendritic growth during directional solidification of hypoeutectic Fe-C-Si alloys

The liquid decanting technique has been used to study the morphology of dendrites in directionally solidified Fe-3.08 pct C-2.01 pct Si alloy. The experimental results indicated that the morphology of primary dendrites in the Fe-C-Si system is very similar to those obtained in some transparent metal model systems and in some other metal systems. In order to study the morphological transition between cellular and dendritic growth, directionally solidified samples were quenched in cold water at various stages of solidification and the morphology was examined on the polished and etched surface. It has been found that when the growth velocity decreased from 326.6 to 0.8 μn/s, the average dendrite tip radius increased from 1.12 to 33.1 μm. At a growth velocity of about 0.65 μm/s, a transition from dendritic to cellular growth occurred. Models for dendritic growth proposed by various investigators have been briefly reviewed and compared with the present experimental results. Significant disagreements were found for some of the available theoretical models. Possible explanations have been given for these disagreements.     

单向凝固Fe—C—Si共晶合金的组织与性能

本文研究了单向凝固Fe-C-Si共晶合金的凝固速度ν,对组织及纵向力学性能的影响,得出ν=2.0 μm/s时,抗拉强度和延伸率均出现峰值;考察了硅含量和基体组织对性能的影响,并分析了拉伸断口形貌。     

An assessment of the Fe-S system using a two-sublattice model for the liquid phase

The strong variation in thermodynamic properties of the liquid phase in some systems is often accounted for by hypothesizing the existence of molecular-like aggregates. It is now suggested that it could also be accounted for in terms of a two-sublattice model. This model is applied to the Fe-S system. A good agreement is obtained with experimental information on the sulfur activity and phase equilibria. The assessment of the Fe-S system was carried out using a computer-operated optimization procedure and the phase equilibria were calculated with a rather general computer program. A. Fernandez Guillermet is, at present he is on leave for studies at the Dept. of Metallurgy, Royal Inst. of Technology, S-10044 Stockholm.     

Nodular graphite formation in vacuum melted high purity Fe-C-Si alloys

This paper describes a study of the cast structure of vacuum melted high purity Fe-C-Si alloys with emphasis on hypoeutectic and eutectic compositions. Nodular graphite was observed to form at high cooling rates and coral graphite at low cooling rates. This result was also confirmed by a limited study on directional solidification of alloys prepared from the same starting materials. The formation of nodular graphite at the high cooling rates was suppressed to near zero by changing the starting iron from 99.94 pct electrolytic iron to an ultra-pure zone refined iron, or by holding the melt at a low super-heat prior to cooling. Chemical analysis showed only that the impurity responsible for nodular formation was present at the low ppm level. An attempt is made to explain the appearance of the various microstructures in terms of the nucleation and growth of nodular graphite, coral graphite and the carbide structure of white iron.     

Physical assessment of the musculoskeletal system

Recently, some investigators have observed elevated concentrations of chloride in the airway surface fluid (ASF) overlying respiratory epithelia from cystic fibrosis (CF) patients compared with ASF overlying non-CF epithelia. Others have shown that this elevated ASF salt concentration can inactivate human beta-defensin-1, an antimicrobial peptide secreted by respiratory epithelia. This could impair the primary epithelial defense against bacteria in the CF airway, thereby forcing a greater reliance on polymorphonuclear leukocyte (PMN)-mediated defenses. Pseudomonas aeruginosa (Psa) flourishes in the CF airway despite the presence of abundant PMN. We therefore investigated whether elevated ASF chloride concentration in CF might also compromise PMN function. We employed a cell-culture model in which halide concentrations and osmolarity were varied independently. We examined the effects of chloride concentration on three aspects of PMN function: recruitment of PMN to the airway (production of interleukin-8 [IL-8]), PMN antimicrobial activity (killing of Psa), and PMN clearance from the airways (apoptosis and lysis). We found that exposure to elevated chloride concentration increased PMN synthesis of IL-8, decreased PMN killing of Psa, and accelerated PMN apoptosis and lysis. In CF airways, elevated chloride therefore could contribute to the increased number of PMN recruited into the airways, the increased survival of Psa, and the increased quantity of toxic mediators released by PMN into the airways. These effects of elevated chloride on PMN function may provide another causal link between loss of cystic fibrosis transmembrane conductance regulator function and CF lung disease.     

Thermodynamic assessment of the Nb-N system

The phase equilibrium and thermodynamic information of the Nb-N system was reviewed and assessed by using thermodynamic models for the Gibbs energy of individual phases. Although there was a large amount of experimental information of the system, heat capacity data of the Nb₂N and NbN were not available either in low or high temperatures. In the present study, low-temperature heat capacity and the^o S ₂₉₈ values were estimated using estimated entropy Debye temperatures. Only the Nb₂N (hcp) and NbN (fcc) nitrides were considered to be the true binary phases and were included in the present evaluation in addition to the N₂ gas, liquid, andα-solid solution (bcc). Three thermodynamic models were used: a two-sublattice model for the solid solution phases, a substitutional model for the liquid phase, and an ideal-gas model for the N₂ gas. The model parameters were evaluated by fitting to the selected data by means of a computer program. A consistent set of parameters was obtained which satisfactorily described most of the experimental and estimated data.     

Thermodynamic assessment of the copper-hafnium system

The thermodynamic properties of phases and phase equilibria in the Cu-Hf system are described with the CALPHAD method. The set of self-consistent model parameters is based on the thermodynamic properties of liquid alloys, intermetallic compounds, and phase equilibria. The excess Gibbs energy of the liquid phase is described using an ideal associated solution model. The models of thermodynamic properties are used to describe possible metastable transformations such as glass formation in rapid quenching from the melt, formation of bulk amorphous alloys, and formation of supersaturated terminal solid solutions.     

美、日、韩及欧盟的合格评定制度简介

综述美国、日本、韩国及欧盟合格评定制度的基本情况.     

Thermodynamic assessment of the CaO-MgO-SiO2 system

The phase equilibrium and thermodynamic information of the CaO-MgO-SiO₂ system at 1 atm was reviewed and assessed by using thermodynamic models for the Gibbs energy of all the phases. The assessment was based on recent assessments of the CaO-MgO, CaO-SiO₂, and MgO-SiO₂ systems. Two thermodynamic models were used: the two-sublattice model for ionic liquids for the liquid phase, and the compound energy model for the solid solution phases. The model parameters were evaluated by fitting to the selected experimental data by means of a computer program, which can accommodate a variety of experimental data. A consistent set of parameters was obtained that sat-isfactorily described most of the experimental information. The models were found to be well-suited for the present system, and only a small number of adjustable parameters were needed. Extensive comparisons were made between the calculations and experimental data. Formerly Research Associate, Royal Institute of Technology     

A thermodynamic assessment of the iron-phosphorus system

Published experimental data for the thermodynamic properties of the different phases of the iron-phosphorus system have been evaluated so as to provide consistency with the reported phase boundaries. The methods of evaluation used are described and the selected data are given together with the corresponding Fe-P phase diagram.