The noble metal alloy database originates from a collaboration between the Spencer
Group Inc., Trumansburg, NY, USA and GTT-Technologies,
The database contains
evaluated thermodynamic parameters for alloys of Ag,
Au, Ir, Os, Pd, Pt, Rh, Ru alloyed amongst themselves and also in alloys
with the metals l, As, Bi, C, Co, Cr, Cu, Fe, Ge, In,
Mg, Ni, Pb, Sb, Si, Sn, Ta, Te, Ti, Tl, Zn, Zr.
The evaluated parameters
in the Noble Metal Alloys Database are based on data collected from publications
and internal project reports or have been assessed as part of the development
of the database.
In only a few cases are
the assessed parameters based on a large amount of experimental information.
For many systems, very few, or even no thermodynamic measurements are available.
This has necessitated use of published phase boundary information only, with
a combination of estimated and optimized mixing parameters to provide a thermodynamic
description of the systems concerned. For some inter-noble metal alloys, where
complete ranges of solid and liquid solutions are observed, the descriptions
should still be fairly reliable. For others, while a reasonable phase diagram
description may have been obtained, the thermodynamic values for the different
phases may have large errors associated with them.
The database provides
a good starting basis for development of data for higher-order noble metal
systems. At the same time, the assessed data it contains for the binary and
ternary sub-systems of Au-Pd-Pt-Sn allow calculations
relevant to dental alloy development.
Noble metals and their alloys have a wide variety of applications and calculations
of relevant phase equilibria in a particular case are important e.g. for optimizing
suitable alloy compositions or predicting reaction products in chemically
of noble metal alloy use are:
- Jewellery and decoration
- Electronic components; micro-electronic contact materials
- Solders and brazes
- Dental alloys
- Fission products
- New minority alloy components, e.g. in turbine alloys
- Scientific equipment, e.g. thermocouples, crucibles, calorimeters
Because of their value,
noble metal alloys undergo extensive recycling. For this reason, information
on dilute ranges of impurity elements in precious metals is important with
respect to different methods of refining. Among such methods are oxygen refining
and some use of halogens. In such cases, the database should be used in conjunction
with the SGTE Pure Substances
Database to take into account relevant condensed and gaseous oxides and
The database will often
be used with one of the noble metals as major component, but in a number of
applications, large concentrations of alloying elements are present. For this
reason, and whenever possible, the assessed parameters in the noble metal
alloys database cover the entire composition range of the alloys involved
(see below for information on relevant ranges for specific alloys).
There are very few ternary
interaction parameters available in the database and it must be realized that
calculation of phase boundaries in higher-order systems by combination of
binary alloy data only may give very unreliable results.
In its present stage of
development, the database can best be used for calculations relating to Ag-,
Au-, Pd- and Pt-rich alloys containing
small amounts (3-5%) of impurity or alloying elements.
The critically assessed values for the Au-Pd-Pt-Sn
system allow theoretical investigation of phase equilibria in certain dental
Most of the binary alloy systems have been assessed over the entire composition
range. Only a few ternary and higher-order parameters are available.
The database is generally valid for the temperature range 300ºC to 2500ºC.
Phase boundaries and thermodynamic properties measured at lower temperatures
may not correspond to the equilibrium state of the alloy, even after very
long annealing times.
The database makes use of the SGTE Pure Element Data and, as such, is compatible
with other SGTE Solution and Application Databases.
In the present assessments, some phases with narrow ranges of composition
have been simplified to compounds with no compositional variation. Others
have been modeled using the compound energy, sublattice formalism.
Systems assessed over complete range of composition:
Ag-Al, Ag-Au, Ag-Bi, Ag-Cu, Ag-Ge, Ag-In, Ag-Ir, Ag-Mg,
Ag-Os, Ag-Pb, Ag-Pd, Ag-Pt, Ag-Rh, Ag-Ru, Ag-Sb, Ag-Si, Ag-Sn, Ag-Ti, Ag-Tl,
Au-As, Au-Bi, Au-C, Au-Cr, Au-Cu, Au-Ge, Au-In, Au-Pb, Au-Pd, Au-Pt, Au-Rh,
Au-Ru, Au-Sb, Au-Si, Au-Sn, Au-Te*, Au-Ti, Au-Tl
Pd-Fe, Pd-Ir, Pd-Ni, Pd-Pb, Pd-Pt, Pd-Ru, Pd-Sn**, Pd-Ti
Pt-Cr, Pt-Rh, Pt-Ru, Pt-Sn, Pt-Ta, Pt-Ti
Sn-In (crude description), Sn-Zn, In-Zn
Systems assessed over
a partial range of composition:
Au-Zn: to 50 at% Zn (crude description)
Pd-In: to 35 at% In
Pd-Zn: to 50 at% Zn (no reliable phase diagram information available)
Pt-In: to 30 at% In
Pt-Zn: only estimated data for the compounds Pt3Zn and PtZn
Pd-Pt-Sn: liquid, (Pd,Pt)2Sn, (Pd,Pt)3Sn2, (PdPt)5Sn3
Pd-Pt-Ti: (Pd,Pt)Ti, (Pd,Pt)3Ti
(Au,Pd,Pt)Sn, (Au,Pd,Pt)3Sn, (Au,Pd,Pt)Sn4
* Please note that the
gas phase should be included in calculations involving the Au-Te system, otherwise
an inverted miscibility gap is predicted in the liquid phase for Te-rich alloys.
** Please note that 2 descriptions of the Pd-Sn
system are provided. The first description uses a simplified, stoichiometric
modeling of the compound phases, which is compatible with the assessed parameters
for the Pd-Pt-Sn and Au-Pd-Pt-Sn
systems. The compound phases denoted by _gtt should be used with the LIQ-gtt
and FCC_gtt phases. The second description provides a more rigorous modeling
of the binary Pd-Sn system. In this case the
phases with no additional definition should be used with the LIQUID and FCC