of liquidus temperature contours for a multicomponent system
application is used for the calculation of a triangular cut in
composition through the phase diagram of a multicomponent, multiphase
system for compositions defined on a triangular grid. The application
works by calculating the phase boundaries at a set of temperatures and
interpreting the results in terms of liquidus contours.
The application can also be used to produce a solidus contours.
asking for the liquidus contours and primary phase fields to be
calculated it is necessary to define a
datafile for the multicomponent system (for three or more components),
to classify any phases required to be absent or identified as
giving rise to miscibility gaps and to specify the pressure. All this
can be set up using the normal APPLICATION commands within MTDATA.
Also it is necessary to define the range of temperatures to be covered
by the scan for the liquidus valleys
range t 500 1200 20 !
third value here represents the contour step interval in temperature.
The number of contours calculated by this application is limited to 55.
For most purposes a value of 50 for the step interval will be
sufficient but for low melting systems where great complexity may arise
over a narrow temperature range, a smaller
value might be more appropriate.
application is designed for a multicomponent system (ie with at least
three components). The following example, however, is for a three
component system. In this case the ternary section is identical to a
the liquidus projection for an ordinary ternary diagram. To calculate
sections in higher order systems it is necessary simply
to add more components to the composition groups.
set 'A' 0.9998 0.0001 0.0001 !
'B' 0.0001 0.9998 0.0001 !
'C' 0.0001 0.0001 0.9998 !
density of calculations is set through use of the user variable
"number_of_steps" (maximum of 100).
the corners of the diagram assigned to the composition groups.
user_v(group_top) 'B' !
user_v(group_lower_right) 'C' !
calculations to be carried out in regions where phase boundaries meet.
This can be turned off
using the "refine" user variable. By default this variable is set to 1.
However if extra calculations
are not required the change can be initiated with:
set user_v(refine) = 0 !
is initiated by entering the compute command.
refinement to the calculations is possible by using the user variable
"defn_method". By default the value of "defn_method" is set to 0 and
the calculations proceed assuming that it is
the boundary at the highest temperature that is required. However if
"defn_method" is 1 then the user
is asked to define whether a LIQUIDUS or SOLIDUS surface is required
and then to categorise
each phase according to whether it should be treated as a liquid or as
a solid or to be ignored with respect to finding a phase boundary.
"defn_method" is 2, further refinement is possible:
set user_v(defn_Method) = 2 !
user variables, Liq_Solidus, liq_phs_nos and ign_phs_nos provide the
user variable Liq_Solidus allows a resticted set of the available lines
to be calculated and plotted, liq_phs_nos allow a particular phase (or
phases) to be assigned as the liquid phase and ign_phs_nos allows
certain phases to ignored in terms of the definition of the phase
boundaries although still present in the calculations.
the liquidus curve is calculated defined as the highest temperature at
which a solid is still present or at which a liquid miscibility gap is
1 just the liquidus curve is required
defined as the highest temperature at which a solid is still present
2 just the solidus curve is required
defined as the highest temperature at which no liquid is present.
3 all boundaries are required except those
corresponding to those phases that are to be ignored, defined by the
user variable ign_phs_nos
user variables liq_phs_nos and ign_phs_nos should be entered within
quotes. If a list of numbers is
given they be separated by + signs. Multiple numbers for liq_phs_nos
both liquid and gas phases to be assigned as high temperature phases eg
projections may also be calculated using other MTDATA applications ie. LIQPROJ and LIQSECT. They
use different ways to delineate the liquidus valley. LIQSECT may give
better indication of the primary phase boundaries for the liquidus but
take longer than LIQCONT while LIQCONT may give better temperature
contours. LIQPROJ is limited to ternary systems.