MTDATA – Phase Diagram Software from the National Physical Laboratory

 

 

 

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Ternary

Introduction

The TERNARY allows ternary phase diagrams (ie for three component systems) to be calculated and plotted for a variety of temperatures. The TERNARY module uses MULTIPHASE to carry out the calculation of phase equilibria and as such allows a wide combination of phases such as alloys, molten salts, gases, aqueous solutions, slags, mattes and pure stoichiometric substances.

Data for the calculations are retrieved either from specified databases or from a datafile prepared in advance. This datafile would normally have been generated from the databases by means of the ACCESS module or from within TERNARY itself. The databases will depend on the installation.

After the temperature has been fixed and an initial composition has been chosen either by means of the graphics cursor or use of the SET command, the calculation and plotting are entirely automatic; a complete plot, consisting of the calculated tie lines and fitted phase boundaries, is guaranteed if the starting point is well chosen and all two- and three- phase regions are adjacent. With less straightforward diagrams, some judgement is required as to whether:

(a)  the starting point is appropriate,
(b)  the diagram is really complete after the automatic plotting process has terminated and
(c)  whether a search for miscibility gaps should be carried out during the calculations.

The program allows the exclusion of some phases from the equilibrium system, so that metastable systems can be investigated.

The numerical results of the calculations for each diagram are automatically stored in a ternary results file. This allows diagrams to be replotted with the option to rearrange the order of the components and to magnify a portion of the diagram for detailed study of a particular area. A facility for labelling phase fields also exists, and further annotation or experimental data may be superimposed on a replotted diagram from information stored in a data file.

Graphical output is sent both to the screen and to a file so that the contents can be routed to a local plotter, either from within the program or by using operating system commands.

Brief summary of commands

DEFINE allows the user to define the system to be studied in terms of the three components. allows the user to name the datafile from which the data are to be retrieved or to define the system to be studied in terms of the three components, in which case the data are retrieved from a named database. The datafile must be in the MTDATA Multiphase format (file extension ".mpi") and should preferably have been retrieved in advance by means of the ACCESS module or from within TERNARY or an equivalent module. When a database search has been performed, the data for the system under study are written to a user-defined or default file. The file name together with the date and time of plotting are displayed in the top left hand corner of the finished diagram.

LIST displays the current definition of the problem in terms of:

(a) the status of the elements, components, substances or phases present
(b) the temperature and pressure/volume set by the user.
(c) whether the diagram is to be plotted in terms of mole or mass fraction and the starting compositions for calculations if defined using the SET command.

CLASSIFY allows the status of individual phases or substances to be classified as NORMAL (present) or ABSENT from the calculation. The number of miscibility gaps potentially present may also be specified if they are to be taken into account in the calculation.

SET allows the user to specify the temperature and pressure to be used for the calculation, and whether the ternary plot produced is to be calibrated in mass fraction or mole fraction. A composition may also be specified, in terms of mole fraction or mass fraction, which acts as either the start point for phase diagram calculations or as the centre of any replotted magnified diagram.

COMPUTE initiates the computation of the ternary diagram at the temperature specified in SET TEMPERATURE. If a starting composition has not already been set, the graphics cursor will appear and should be moved to the required starting point. The calculation and plotting of the diagram is entirely automatic for straightforward systems. The graphics cursor reappears on completion of the plot and, if desired, may be used to label the phase fields or to restart the calculation in a different region of the diagram. Output is sent simultaneously to the screen and a system scratch file. Hard copy output can be obtained by using the command LASER which copies the contents of this file to your local plotting device.

REPLOT allows a previously calculated diagram to be replotted at the terminal from tie line information stored in a ternary results file. Various options are available to allow magnification of a chosen portion of the diagram, rearrangement of the component axes, selection of weight or mole fraction composition scale and the addition of labelled experimental data and other annotation stored in a file.

LASER sends a copy of any diagrams plotted on the screen to a local plotting device if available.

RETURN takes the user out of TERNARY back to the module level.

<"Macro name"> runs a macro taken from a file. The name of the file should be entered in quotes. Commands can also be passed through to the operating system by prefixing them with a $ (dollar sign). The dollar sign and operating system command should be entered within quotes.

Further Information

A gentle introduction gentle introduction to using the options available in TERNARY contains annotated examples, each directed towards achieving a particular outcome, showing typical combination of commands which would be necessary to achieve that end.

A simple summary of the commands available can also be used as an index to obtain more detailed help about each command.

Experimental data can be overlayed onto calculated ternary diagrams.

 

Updated 2 July 2010