A method is presented for calculating both the macroscopic strains and the crystallographic bias which develop when a polycrystalline sample of austenitic steel is transformed into bainite or martensite under the influence of an applied stress or a system of stresses. Any texture present in the austenite prior to transformation is taken into account, as is the detailed crystallography of the transformation. Comparisons with experimental data are encouraging. A strong correlation has been observed between the proportion of the driving force for transformation that is attributed to stress and the extent of variant selection.

Crystallographic texture of stress-affected bainite

Proceedings of the fourth calphad meeting Workshop on computer based coupling of thermochemical and phase diagram data held 18–22 August 1975 at the National Bureau of Standards, Gaithersburg, Maryland☆

A data base is being developed for calculation of quasi-binary and quasi-ternary phase diagrams of ceramic systems (1–3). Previous segments of this base cover combinations of Cr2O3, MgO, Al2O3, Fe2O3, Fe3O4, “FeO”, SiO2, CaO, Si3N4 and AlN. Lattice Stability, Solution and Compound Phase Parameters were derived covering the liquid, spinel, corundum, periclase, crystobalite, tridymite, quartz, hexagonal and beta prime phases which appear in the binary systems composed of pairs of these compounds. Compound phases formed from specific binary combinations of these compounds (i.e. MgO·Cr203) were also characterized. This description is based on observed thermochemistry and phase diagrams for the binary systems of interest. Selected ternary systems have been computed based on the foregoing data base for comparison with experimental sections in order to illustrate the usefulness of the data base. The present paper extends the data base to cover BeO, Y2O3 and Ce2O3 additions. Moreover, ternary sections in the SiO2-MgO-Si3N4, SiO2-Y2O3-Si3N4 and SiO2-Ce2-O3-Si3N4 were calculated between 1900K and 2100K for comparison with experiment.

Calculation of quasibinary and quasiternary oxyntiride systems-IV☆☆☆

Most metallic alloys contain small concentrations of solutes because they are sufficient to achieve amazing properties on a grand scale of production and utilisation. In the early 1980s, a different concept was introduced that involved mixing large concentrations of solutes in roughly equal amounts so that there is no predominant solvent. When this happens, the degree of disorder increases and this can contribute to thermodynamic stability so that the alloy remains as a single phase in spite of the usual tendency of decomposition as solubility limits are exceeded. Whether or not this leads to properties that are unique and affordable remains to be seen, but it is clear that there are possibilities that deserve investigation.

High entropy alloys

Aluminum-based alloys are widely used in different industries. We need to know the physical and chemical properties of these materials to improve the methods to produce them and to identify their optimal service conditions. Hence, the objective of this paper is to examine the thermodynamic properties of Al–Ti(Zr, Hf) binary melts by isoperibolic calorimetry at 1770 ± 5 K and 1790 ± 5 K. The experimental and data processing methods are described in [1]. Aluminum AV000 (99.999%), titanium, zirconium, and hafnium (99.9%) were used. Aluminum was placed into an yttria-lined corundum crucible in a massive molybdenum block. The calorimeter was calibrated against aluminum at the beginning of the experiment and against tungsten A2 (99.96%) at the end. Prior to the experiment, the calorimeter was warmed up under constant evacuation using forevacuum and diffusion pumps up to 773 K. After that, the chamber was filled with purified argon. The relative errors of the partial and integral mixing enthalpies were ±10 and ±2%, respectively. The reproducibility of the results is within 3%. During the experiment, we recorded variations in temperature that occurred when group IVb metal samples were introduced into liquid aluminum. The chamber heating rate is limited by the evacuation speed. The temperature variations during the experiment were recorded with a self-recorder and thermal effects were determined with the gravimetric method. The partial mixing enthalpies for Ti, Zr, Hf and integral mixing enthalpies for Al–Ti(Zr, Hf) binary melts are shown in Fig. 1. The thermodynamic properties of Al–Ti(Zr, Hf) binary melts are compared with similar data [2–8]. There are few experimental data on the thermodynamic properties of Al–Ti melts over a wide concentration range. At low concentrations, all mixing enthalpies of Al–Ti melts correlate with each other within experimental errors (Fig. 2a). However, the formation enthalpies turned out to be more exothermal at x Ti > 0.15 than Δ m H [3] determined calorimetrically at 2000 K. This is evidence of the temperature dependence of the mixing enthalpies of

Thermodynamic properties of melts in Al–TI(Zr, Hf) binary systems

When chemical thermodynamic calculations are applied to the evaluation of· metallurgical processes, it is essential that reliable data are used in order to reach valid conclusions. The compilation of such data from raw experimental results which are reported in the literature is a highly skilled operation. All aspects of the skills involved are described in the present article, including available methods for estimating unknown data. It is desirable that fully self-consistent data should include reliable phase diagram information when available, and the relationships between thermodynamic data and phase equilibria are described. A review is given of the current position in the calculation of phase equilibria for multicomponent alloy systems, employing data from binary systems. The storage of data in computer data banks is discussed and the particular NPL data bank which stores metallurgical thermodynamic data is described. Finally, a review of recent examples in which thermodynamic calculations h...

W. Slough

Papers

Provision and Use of Thermodynamic Data for the Solution of High-Temperature Practical Problems