Enthalpy of formation of intermetallic phases from Al–Zr system determined by calorimetric solution method
Journal of Thermal Analysis and Calorimetry
Enthalpy of formation of intermetallic phases from Al-Zr system determined by calorimetric solution method
Tomasz Macia˛ g 0 1
Intermetallics 0 1
0 Department of Extractive Metallurgy and Environmental Protection, Silesian University of Technology , Krasin ́skiego 8, 40-019 Katowice , Poland
1 & Tomasz Macia ̨g
Intermetallic phases represent a group of materials of unique properties. Many of those materials have found practical application, whereas others are still intensively examined. There are ten stable intermetallic phases in Al-Zr system, among which few are prospective materials to work at elevated temperature, nuclear reactors, etc. On top of that, researches are focused on obtaining amorphous phases, nanoparticles and zirconium-based pressure pipes covered with aluminum. As a result, better understanding of thermal effects accompanying those compounds formation becomes crucial. In this paper, solution calorimetry method was used for determination of formation enthalpy DfH of intermetallic phases from Al-Zr system at room temperature (298 K). Experiments were conducted using test station built by author. Material used as bath was aluminum. Additionally, alloys preparation methodology was described and presented. Calorimetric measurements were taken on phases: Al3Zr, Al2Zr, Al3Zr2, AlZr, Al2Zr3, AlZr2 and AlZr3. Heat of dissolution of zirconium in aluminum bath at temperature 1073 K was determined experimentally and was equal to - 244.5 ± 5.4 kJ mol-1. Obtained results of enthalpy of formation were summarized and compared with the literature data.
Modern material engineering keeps searching for materials
being able to work in various conditions; therefore, a lot of
attention is put for intermetallic phases. Those phases
characterize with ordered structure and often
stoichiometric composition. As a result, properties are substantially
different from alloys in which they appear. They are
described as indirect materials among ceramics and alloys,
mostly due to brittleness at room temperature and high
melting point, resistance to oxidation and corrosion,
elevated temperature strength and relatively low density.
Particularly, interesting intermetallic phases from practical
point of view are those containing aluminum and transition
metals (Ni, Ti, Zr, Hf, V, Nb, Ta) [
]. Some of them
have found practical application long time ago, e.g., NiAl
for coating materials or Ni3Al for high-temperature
structural materials [
]. Others, like aluminum–zirconium
intermetallics, may be potentially applied in thermal
nuclear reactors [
], also extensive work on the
Al–Zrbased amorphous and nanocrystalline alloys has been
]. Phase Al3Zr is desirable candidate for
high-temperature structural applications [
Al–Zr system shown in Fig. 1 is one of the most
complicated of all the transition metal aluminide binary phase
]. According to the evaluation of
Murray et al., there are ten stable intermetallic phases:
Al3Zr, Al2Zr, Al3Zr2, AlZr, Al4Zr5, Al3Zr4, Al2Zr3, Al3Zr5,
AlZr2 and AlZr3; all of which experimentally are found to
have extremely narrow concentration ranges [
]. Two of
them Al4Zr5 and Al3Zr5 are high-temperature phases.
Available in the literature crystallographic data of Al–Zr
intermetallics are listed in Table 1 [
This paper is focused on thermodynamic data,
specifically on thermal effects accompanying formation of
intermetallic phases from Al–Zr system. The literature data
present minor results obtained from experiments, whereas
major of them originate from computational methods. In
this work, high-temperature calorimetric solution method
for determination of formation enthalpy DfH of
intermetallic phases from Al–Zr system at room temperature
(298 K) is proposed. Calorimetric measurement allows for
determination of molar enthalpy of formation that is one of
the most important thermodynamic data used in computing
and phase diagrams optimization. Formation enthalpy is
determined using high-temperature solution calorimeter
with indirect method. For binary alloys AB, value of
enthalpy of formation results from the difference between
heat effects accompanying dissolution of A, B components
and AB alloy separately in metallic bath. It is worth to
mention that the alloy obtained before the calorimetric
experiment and its components are dissolved in the same
type of solvent. In presented research, aluminum bath is
used, and additionally preparation of intermetallic phases
from Al–Zr system as well as results analysis is described.
High-temperature phases Al4Zr5 and Al3Zr5 are not part of
Phases preparation and analysis
Preparation of alloys with precisely defined stoichiometry
from pure components requires application of proper
melting method. One of the most commonly used is
melting in electric-arc furnace. Disadvantage of this
method is poor stirring, inhomogeneous structure and
composition of alloy resulting from high-temperature
]. Therefore, in this work, levitation melting was
selected as method of alloying. It allows for obtaining
homogeneous casts without segregation effects thanks to
fast crystallization. Additional advantage is also high purity
of alloys resulting from no contact with crucible material
Pm3 m (221)
which could contaminate sample [
]. Levitation furnace
uses inductive heating effect which bases on heat
generation during eddy current flow, induced from
electromagnetic induction phenomenon in elements magnetically
coupled. For the phenomenon of levitation, it is necessary
to create gradient and the value of magnetic component of
the field to compensate the mass of metal and to keep it in
the stable position by magnetic forces. In order to form the
field of particular geometry, appropriately shaped coil is
required. It is usually made from copper tube and is
intensively water cooled. The coil is powered by
highfrequency generator, with an output of at least few
kilowatts. Then, in the central part of the coil the field is
weakest, and the metal is pushed to this zone occupying
more or less stable position [
For obtaining intermetallic phases from Al–Zr system,
metals of high purity were used: aluminum 99.999% and
zirconium 99.99%. Based on stoichiometry of phases, eight
analytical samples in particular mass ratio were prepared.
They were melted in induction levitation furnace, which
diagram is presented in Fig. 2. Furnace is equipped with
high-frequency generator GIS-10 (10 kW in 415 kHz). It
allows for metal casting of approximately 2 cm3 volume.
Fig. 2 Diagram of the laboratory levitation melting apparatus: 1—
metal sample, 2—turning table, 3—manipulating rod, 4—gas inlet,
5—coil, 6—generator of high-frequency current, 7—quartz tube, 8—
metal droplet, 9—looking window, 10—mirror, 11—pyrometer, 12—
copper mold, 13—gas outlet, 14—water heating
All casts were performed in protective atmosphere of argon
(N6.0). Within seconds, metals were melted during which,
intensive stirring and overheating was occurring. Short
time of melting using levitation method allowed for
minimizing of oxidizing risk of alloys. After reducing power of
generator, melted metal felled on water-cooled cooper
mold, shaped in inverted cone and immediately solidified
with the same shape. Mass decrement of alloy after casting
compared to metallic charge was negligible.
Due to overcooling, amorphous structure in alloys
occurred. Tendency to the formation of amorphous phases
during overcooling on the example of AlZr3 was presented
by Ma [
]. Samples were submitted to long-lasting
annealing at elevated temperature. Casts were cut with
electro-erosion saw in half and vacuum-sealed in quartz
capsules. They were placed on ceramic pad in order to
separate samples from quartz wall. Conoidal shape of
samples reduced also contact with pad. Alloys were heated
in resistance furnace at temperature 1123 K for 672 h
(28 days). Cooling was performed together with furnace.
Subsequently, phase composition was verified using
X-ray phase analysis, performed on X-ray diffractometer
PW 1710 (Philips). Filtered radiation of CoKa was used for
measurement. Analysis results are presented in Table 2. In
majority of samples, apart from identified phases from Al–
Zr system, presence of aluminum was revealed. It was
taken into consideration while computing accompanying
enthalpy of formation measurements. Also presence of
other phases than investigated is stated. Its quantity is
negligible in case of samples: Al3Zr, Al2Zr and Al2Zr3;
only in case of samples marked as AlZr and Al3Zr4, content
of expected phase is below 95%. Sample AlZr was used in
calorimetric measurements; on contrary, sample Al3Zr4
was rejected due to significant presence of
high-temperature phase Al3Zr5. X-ray pattern of sample AlZr is
presented in Fig. 3, and that of sample Al3Zr4 is shown in
Fig. 4. In parallel, metallographic specimen was prepared,
which was analyzed on scanning electron microscope
PHILIPS XL30 integrated with energy-dispersive X-ray
spectrometer LINK ISIS (EDS). Figures 5 and 6 present
images of heated alloys obtained in the light of backward
scattered electrons (BSE) and results of chemical
composition analysis obtained using EDS analysis. In case of
AlZr sample are visible clear precipitations in form of
dendrites (Fig. 5). Dark places visible on microstructure of
Al3Zr4 sample are pores created during fast solidification of
sample (Fig. 6).
Measurements of enthalpy of formation DfH at temperature
298 K of intermetallic phases from Al–Zr system were
taken on test station equipped with high-temperature
solution calorimeter (Fig. 7). It consists of calorimeter,
vacuum pump set, bottle with argon of spectral purity
(N6.0), module for signal recording and computer. The
calorimeter is a pipe furnace containing calorimetric block
that is locked in casing shaped as barrel. It is connected
with locks used for entering of samples, set of valves
ensuring protective atmosphere during measurements,
thermoelements and also temperature controllers. Detailed
description of the calorimeter as well as problems related to
calibration of the device can be found in other papers of the
]. In this work, only most important element
that is calorimetric block will be discussed. It consists of
elements presented in Fig. 8.
Alundum crucible (1 in Fig. 8) has internal diameter
around 35 mm and can contain aluminum bath of 50 g
mass. Mass of examined samples represents minimal part
of the bath. Small change in degree of fulfillment of
crucible during experiment is crucial in calorimetric
experiment. Directly under crucible bottom is presented
thermopile (2 in Fig. 8) consisting of around seventy
thermocouples type S (PtRh10-Pt), connected in series.
Thermopile is used for measuring thermal effect
Position [°2θ] (Cobalt (Co))
Position [°2θ ] (Cobalt (Co))
accompanying dropping the sample into the bath. Alundum
stirrer (3 in Fig. 8) is used for obtaining homogeneous
composition of bath bulk and increasing measurement
accuracy. The sample is dropped into the bath by the tube
(4 in Fig. 8). Temperature of calorimetric block is
measured with thermocouple type N (NiCrSi–NiSi) (5 in
Fig. 8). Main body of calorimetric block (6 in Fig. 8) is
made of heat-resisting steel. It is placed in heat-resisting
Fig. 8 Calorimetric block scheme: 1—alundum crucible,
2—thermopile, 3—alundum stirrer, 4—sample inlet, 5—thermocouple, 6—
block housing, 7—block container, 8—furnace, 9—sample inlet from
steel container (7 in Fig. 8), which is located inside
calorimeter furnace (8 in Fig. 8) and is characterized by
significant thermal inertia.
Measurement principle of thermal effects in solution
method relies on the change in the temperature of a bath,
into which sample is dropped. Base temperature
(temperature of calorimetric block between single measurements)
in one series of measurement remains stable.
Determination of formation enthalpy with use of high-temperature
solution calorimeter bases on comparison of heat effects
accompanying dissolving of alloys and its components in
metallic bath. For binary alloys, it can be presented as:
Df H ¼ xADHef: B
A þ xBDHef:
where DfH—formation enthalpy of the alloy; xA, xB—
concentrations (mole fractions) of the alloy components;
DHAef:; DHBef:; DHAefx:A BxB —heat effects accompanying
dissolution of the components and the alloy in the bath.
It is worth mentioning that thermal effect consists of:
heating, melting and solving of the sample in the bath.
Enthalpy of formation is determined for temperature, from
which sample is dropped into the bath.
In order to prepare samples for calorimetric measurements,
it was necessary to cut it using electro-erosion saw so that it
could fit dosing pipe of internal diameter approx. 4 mm.
Preparation of the experiment started with placing of
aluminum roll (of 99.99% purity) in the crucible, closing of
the device and triple gas pumping out from the interior of
calorimeter with use of turbomolecular pump; alternately,
argon was introduced. All experiments were conducted in
argon atmosphere. In parallel, temperature of aluminum
bath was raised up to 1073 K. Device was left for 24 h in
order to obtain equilibrium state that is being identified as
stabilized baseline observed on computer monitor. Next,
stirrer was installed, and device was ready for experiment.
During the first measurements of the series, the device was
calibrated by dissolving aluminum samples; in this manner,
amount of energy per conventional unit was determined
]. After calibration, experimental samples were dropped
into aluminum bath from room temperature (298 K). Heat
effect was registered by computer, and special software
allowed to determine value of enthalpy accompanying
dissolving samples in bath as well as enthalpy of formation
Table 3 presents results of formation enthalpy DfH of
intermetallic phases from Al–Zr system determined with
solution calorimetric method. Partial dissolving heat of
zirconium in liquid aluminum at temperature 1073 K
(Table 4) was evaluated in own measurements, that is
critical for formation enthalpy of intermetallic phases from
Al–Zr system determination. The heat effect accompanying
dissolving of the second compound (aluminum) was
considered when series of calibration were performed.
Calculations were corrected also taking into account the
presence of Al in samples, which was stated based on phase
Enthalpy of formation is one of the most important
thermodynamic data used for computing and optimization
of phase diagrams. Among various methods of determining
this value, the calorimetric measurement is one of the most
precise ones. Due to the difficulty of measuring the
formation enthalpy of alloys, many thermodynamic data
available in the literature are based only on computational
In Table 5, results obtained in this work are compared
with the literature data, among which experimental data are
] as well as results obtained with
computational methods, mostly from CALPHAD
procedure (CALculations of PHAse Diagrams) [
Miedema’s Model [
]. Kematick and Franzen [
combined several measurements to obtain enthalpies of
formation of compounds Al3Zr5, Al2Zr3, Al4Zr5, AlZr,
Al3Zr2, Al2Zr and Al3Zr. They measured the equilibrium
vapor pressure of Al by the Knudsen-effusion technique.
The enthalpies of formation of the compounds were
evaluated by means of the second- and third-law methods.
Kematick and Franzen results were adjusted by
Murray et al. [
] since they did not take into account the
difference between the free energies of the liquid and solid
phases of pure Al above its melting point. Murray also
estimated the associated error to be ± 4 kJ mol-1.
Meschel and Kleppa [
] measured standard enthalpies of
Al2Zr and Al3Zr by direct synthesis calorimetry at 1473 K.
Klein et al. [
] determined standard enthalpy of formation
for the AlZr2 phase also from calorimetric measurements.
There are no experimental data for phase Al3Zr4 that is
particularly interesting, considering difficulty in obtaining
it, that is presented in this work.
Results of formation enthalpy DfH of intermetallic
phases from Al–Zr system, presented in this paper, show
good compatibility with experimental data available in the
literature. Only in case of phase AlZr, distinct difference is
visible. It can be a result of a presence of small quantity of
other phases like Al3Zr2, Al3Zr4 and Al3Zr5, which was
stated during X-ray analysis (Fig. 3). The best
compatibility with computational method is recognized with work
of Wang et al. [
]. Differences occur in case of phases
AlZr3 and AlZr2, still it is worth to emphasize that results
of formation enthalpy from this paper represent
experimental data shown for the first time.
r .6 ± ± .4 .1 .5 .5
Z 1 1 9 8 9 0 8
3 5 4 4 4 4 4 4
A - - - - – - - - –
E E E E E C C C C
5 ± ±
Z 4 2
4 4 5
r3 .0 ± ±
Z 9 1 9
2 4 4 4
A – - - – – - - -
A – – – – – - – - –
Z m .1
– J 3
se A - - - – – - - -
m A – - - – – - - -
le HDf r2 .1 .8 .4 .4
b 6 6 3 8 5
tfsa iton lZA 5- – – – – 3- 3- 4-
For the preparation of eight intermetallic phases
stable at room temperature from Al–Zr system, melting
in levitation furnace was used. Phase analysis XRD
indicated that only in case of alloy denoted as Al3Zr4 it
was impossible to obtain sufficient intermetallic phase;
therefore, it was not taken into consideration in
High-temperature solution calorimeter was used in
order to determine formation enthalpy DfH of
intermetallic phases from Al–Zr system at room
temperature (298 K). Partial dissolving heat of zirconium in
aluminum at temperature 1073 K which is crucial
value in described experiment was evaluated as
- 244.5 ± 5.4 kJ mol-1.
The value of formation enthalpy DfH of intermetallic
phases from the Al–Zr system at 298 K was
determined: Al3Zr (- 51.6 ± 1.2 kJ mol-1), Al2Zr
(- 56.3 ± 2.2 kJ mol-1), Al3Zr2 (- 59.6 ± 2.4
kJ mol-1), AlZr (- 71.3 ± 4.4 kJ mol-1), Al2Zr3
(- 49.0 ± 3.1 kJ mol-1), AlZr2 (- 56.1 ± 3.1 kJ mol-1)
and AlZr3 (- 43.6 ± 2.3 kJ mol-1).
Obtained results were compared with data available in
the literature. For the first time, experimental value of
enthalpy of formation for phases AlZr3 and AlZr2 was
Presented calorimeter, thanks to applied preheating
intermediate container, can be used in the future for
determination of formation enthalpy of
high-temperature phases from Al–Zr system that is: Al4Zr5 and
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1. Sauthoff G . Intermetallic compounds . In: Westbrook JH , Fleisher RL , editors. vol. 1 . Wiley: New York, NY; 1994 . p. 991 .
2. Cahn RW . Combining metals and sciences: ways of investigating intermetallics . Intermetallics . 1998 ; 6 : 563 - 6 .
3. Ye HQ . Recent development in high temperature intermetallics research in China . Intermetallics. 2000 ; 8 : 503 - 9 .
4. Stoloff NS , Liu CT , Deevi SC . Emerging applications of intermetallics . Intermetallics . 2000 ; 8 : 1313 - 20 .
5. Sikka VK , Deevi SC , Viswanathan S , Swindeman RW , Santella ML . Advances in processing of Ni3Al-based intermetallics and applications . Intermetallics . 2000 ; 8 : 1329 - 37 .
6. Schulson EM . Intermetallic compounds . In: Westbrook JH , Fleisher RL , editors. vol. 2 . Wiley: New York, NY; 1994 . p. 133 - 45 .
7. Ibrahim EF , Cheadle BA . Development of zirconium alloys for pressure tubes in CANDU reactors . Can Metall Q . 1985 ; 24 : 273 .
8. Ma E. Amorphization and metastable polymorphs of ordered intermetallics Zr3Al and Ni3Al . J Mater Res . 1994 ; 9 : 592 - 7 .
9. Sheng HW , Lu K , Ma E. Amorphization of Zr-Al solid solutions under mechanical alloying at different temperatures . J Appl Phys . 1999 ; 85 : 640 .
10. Inoue A , Zhang T , Chen MW , Sakurai T , Saida J , Matsuhita M. Formation and properties of Zr-based bulk quasicrystalline alloys with high strength and good ductility . J Mater Res . 2000 ; 15 : 2195 - 208 .
11. Tamim R , Mahdouk K. Thermodynamic reassessment of the AlZr binary system . J Therm Anal Calorim . 2017 . https://doi.org/ 10.1007/s10973-017-6635-3.
12. Murray Z , Peruzzi A , Abraita JP . The Al-Zr (aluminum-zirconium) system . J Phase Equilibria . 1992 ; 13 : 277 - 90 .
13. Ghosh G , Asta M . First-principles calculation of structural energetics of Al-TM (TM = Ti, Zr, Hf) intermetallics . Acta Mater . 2005 ; 53 : 3225 - 52 .
14. Sypien ´ A. Modern materials prepared with the use of levitation melting method in the magnetic fields . In: Institute of Metallurgy and Material Science Polish Academy of Sciences. E-learning platform . 2007 . http://www.imim.pl/PHD/www.imim-phd.edu.pl/ contents/Relevant%20Articles/Anna%20Sypien. pdf. Accessed 13 Dec 2017 .
15. Czeppe T , Sypien´ A , Korznikova G , Korznikov A . Microstructure of the Ni-W solid solution prepared by levitation and after high pressure torsion severe plastic deformation . Sol State Phenom . 2012 ; 186 : 104 - 7 .
16. Peyrade JP , Garigue J , Astie P . Preparation of alloys of iron and substitutional elements by levitation techniques . Mem Sci Rev Met . 1974 ; 71 : 377 - 82 .
17. Foryst J , Przybyło W. The effect of the solidification conditions on hydrogen content in cobalt . Microchim Acta . 1985 ; 1 : 59 - 67 .
18. Macia˛g T, De˛bski A , Rzyman K. The studies of assumption accompanying the calibration of high-temperature solution calorimeter . Arch Metall Mater . 2011 ; 56 : 585 - 92 .
19. Macia˛g T, Rzyman K. New possibilities of recently constructed high-temperature solution calorimeter . J Therm Anal Calorim . 2013 ; 113 : 189 - 97 .
20. Kematick RJ , Franzen HF . Thermodynamic study of the zirconium-aluminum system . J Solid State Chem . 1984 ; 54 : 226 - 34 .
21. Meschel SV , Kleppa OJ . Standard enthalpies of formation of 4d aluminides by direct synthesis calorimetry . J Alloys Compds . 1993 ; 191 : 111 - 6 .
22. Klein R , Jacob I , O'Hare PAG , Goldberg RN . Solution-calorimetric determination of the standard molar enthalpies of formation of the pseudobinary compounds Zr(AlxFe1-x)2 at the temperature 298.15 K. J Chem Thermodyn . 1994 ; 26 : 599 - 608 .
23. Saunders N. Z. Calculated stable and metastable phase equilibria in Al-Li-Zr alloys . Metallkd . 1989 ; 80 : 894 - 903 .
24. Wang T , Jin Z , Zhao JC . Thermodynamic assessment of the AlZr binary system . J Phase Equilibria . 2001 ; 22 : 544 - 51 .
25. Boer FR , Boom R , Mattens WCM , Miedema AR , Niessen AIC . Cohesion in metals . Amsterdam: North Holland; 1988 .