High-temperature Isoperibolic Calorimetry Research Articles

Mixing enthalpy of the Co–Ti–Hf liquid alloys and regularities of the function change in the row of the ternary (Co, Ni, Cu)–Ti–Hf glass-forming melts

The partial molar mixing enthalpies of titanium and hafnium in liquid Co–Ti–Hf alloys were studied at 1900 K by high-temperature isoperibolic calorimetry along xCo/xHf = 3 and xCo/xHf = 3 sections. The partial mixing enthalpies of undercooled liquid titanium and hafnium in liquid alloys and the integral mixing enthalpy are negative over the studied composition range. The thermodynamic mixing functions of liquid (Co, Ni, Cu)–Ti–Hf alloys were modeled in the framework of the associate solution model. Regularities in the change of thermodynamic mixing functions in liquid glass-forming (Co, Ni, Cu)–Ti–Hf alloys are discussed considering donor–acceptor interaction of the components in the melts.

The enthalpies of mixing of ternary liquid Ag-Ca-Ge alloys

Partial and integral enthalpies of mixing of the ternary Ag–Ca–Ge melts were determined for the first time by the high-temperature isoperibolic calorimetry at 1300–1550 K. The experiments were performed for six sections with a constant ratio of two components up to the molar fraction of the third component equal to 0.3. The enthalpies of mixing in this ternary system are exothermic values which increase in absolute value from the Ag corner of the concentration triangle towards the constituent binary Ca–Ge system. The minimum value of the integral enthalpy of mixing was obtained for Ca0.6Ge0.4 composition of the Ca–Ge binary system (about –58.00 kJ mol–1). The enthalpies of mixing of the ternary Ag–Ca–Ge melts are calculated for the whole concentration triangle by the Redlich-Kister-Muggianu method, taking into account the term of specific ternary interaction defined from our experimental data. The topology of the isoenthalpies of mixing is determined.

Mixing enthalpies of liquid nickel–gallium alloys

The partial mixing enthalpies of melt components in the Ni–Ga system are measured using hightemperature isoperibolic calorimetry at 1770 ± 5 K in a wide composition range. The partial mixing enthalpy of gallium in liquid nickel is –96 kJ/mol. for infinite dilution, while the same function of nickel in liquid gallium is –75 kJ/mol. The integral mixing enthalpy of liquid alloys in this system is calculated from partial enthalpies for the entire composition range (∆m H min = –32 kJ/mol. at xNi = = 0.5). The mixing enthalpies ∆m H of Ni–B (Al, Ga, In) binary alloys are compared. It is shown that the indicated systems are arranged in the Ni–In → Ni–Ga → Ni–B → Ni–Al series according to the increase in interaction energy of dissimilar components. The ∆m H min values of liquid Ni–B(Al, Ga, In) alloys are compared with the values of electrochemical and size factors.

Thermodynamic properties of Ni-Ga melts

The partial mixing enthalpies of the components (Δm\( \bar H \)i) of the Ni-Ga melts were measured using the high-temperature isoperibolic calorimetry at 1770 ± 5 K in wide concentration interval. The limiting partial mixing enthalpy of gallium in a liquid nickel (Δm\( \bar H \)Ga∞) is −95.5 ± 19.8 kJ mol−1, and similar function of nickel in liquid gallium (Δm\( \bar H \)Ni∞) is −74.5 ± 16.4 kJ mol−1. The integral mixing enthalpy of liquid alloys of this system was calculated from partial enthalpies for the whole concentration area (ΔmHmin = −32.1 ± 2.7 kJ mol−1 at xNi = 0.5). The ΔmH value of liquid nickel-gallium alloys independence of the temperature is confirmed. Enthalpies of formation of liquid (ΔmH) phases of Ni-Ga system were compared with ones for solid (ΔfH) phases of this system. An analysis of d-metals influence on formation energy of Ga-d-Me melts was made using the values of ΔfH for intermediate phases of these systems. The article was translated by the authors.

A calorimetric study and modeling of the enthalpy of mixing of Cu-Fe-V melts

The partial enthalpy of mixing of vanadium in three-component Cu-Fe-V melts was studied at 1873 K along sections with constant x Cu/x Fe ratios of 3, 1, and 1/3 over the composition range x V = 0–0.55 by high-temperature isoperibolic calorimetry. The Muggianu-Redlich-Kister model was used to describe the concentration dependence of the integral enthalpy of mixing of Cu-Fe-V melts over the whole concentration triangle. The contribution of ternary interaction to the integral enthalpy of mixing of Cu-Fe-V melts was calculated.

Partial and integral enthalpies of mixing of Cu-Fe-Ti melts at 1873 K

The partial enthalpy of mixing of titanium in Cu-Fe-Ti melts are studied by high-temperature isoperibolic calorimetry at 1873 K in the composition range xTi = 0–0.6 along three sections with a ratio xFe / xCu = 1/3, 1, and 3. The integral enthalpy of mixing of the ternary melts is calculated by integrating the Gibbs-Duhem equation and is described in terms of the Redlich-Kister-Muggianu model. Function ΔH demonstrates negative values over a wide concentration range. The contribution of a ternary interaction to the enthalpy of mixing of Cu-Fe-Ti melts is mainly positive. The first partial enthalpies of mixing of Al, Sn, Si, Y, Zr, Hf, and Ni with Cu-Fe-Ti melts are negative and indicate an increase of the thermodynamic stability of the liquid phase upon the dissolution of these additions.

Thermodynamic properties of binary Si–Y (transition metal) alloys

The partial (for yttrium) mixing enthalpies (∆ m $$ {\overline H_Y} $$ ) of Si–Y molten alloys are determined using high-temperature isoperibolic calorimetry at 1770 ± 5 K for 0 < x y < 0.2. The integral mixing enthalpies (∆ m H) of Si–Y melts are calculated from these data. The formation of these molten alloys is accompanied by large exothermic heat effects. The generalized values of ∆ m H for molten Si–Y alloys are based on our and literary data. The activities of the melt components are calculated from liquidus coordinates of the Si–Y phase diagram. The values are characterized by very large negative deviations from the Raoult law. Correlation is established between the extremum of the integral mixing enthalpy for melts of silicon with d-metals and electronegativity differences and atomic radii of the alloy components.

Investigation of thermodynamic functions of mixing of Fe-Ti melts

The enthalpy of mixing of Fe-Ti melts is studied by high-temperature isoperibolic calorimetry at 1873 K. The experimental data on the thermodynamic functions of mixing in the melts of the system under study are used to calculate the parameters of the ideal associated solution model. This model is employed to simulate the temperature-concentration dependences of liquid Fe-Ti alloys and to find the features of change in their thermodynamic properties.

Thermodynamic properties of Ge-Y alloys and binary systems of germanium with transition metals

The partial (for yttrium) mixing enthalpies of Ge-Y melts are determined using high-temperature isoperibolic calorimetry at 1780 ± 5 over a concentration range 0 < xY < 0.4. These data are used to calculate the integral mixing enthalpy of the melts. The formation of Ge-Y alloys is accompanied by substantial exothermic effects. The ΔH values for Ge-Y liquid alloys are generalized on the basis of our and literature data. The activities of the components of Ge-Y melts are calculated using the liquidus coordinates of the Ge-Y phase diagram. The values obtained are characterized by very large negative deviations from the Raoult law. The thermochemical properties of Ge-3d-Me melts, dimensional and electrochemical factors, and the occupation of the valence d-orbitals of transition metals are analyzed.

Enthalpy of mixing of liquid Cu-Ti-Zr alloys

The enthalpy of mixing of liquid Cu-Ti-Zr ternary alloys is studied by high-temperature isoperibolic calorimetry at 1873 K along three ray sections characterized by the ratios xZr: xCu = 3: 7, xTi: xCu = 3: 7, and xZr: xTi = 1 at xCu = 1−0.4. The isotherm of the integral enthalpy of mixing of these melts is described in terms of the Redlich-Kister-Muggianu model. Along with the substantial contributions of binary copper-titanium and copper-zirconium interactions, the contribution of a ternary interaction to the enthalpy of mixing of liquid Cu-Ti-Zr alloys also exists. The first partial enthalpies of mixing of Ni, Al, Si, Sn, and Y with the melts are studied to determine the character of the interaction between the ternary Cu-Ti-Zr melts and metal additions that facilitate amorphization upon melt quenching. The introduction of these metals into the ternary melts is shown to increase their thermodynamic stability.

Enthalpy of mixing of liquid (gallium–gadolinium–silicon) alloys measured by high-temperature isoperibolic calorimetry

The partial enthalpy of mixing of gadolinium ( Δ mix H ¯ Gd ) in liquid ternary (gallium + gadolinium + silicon) alloys has been measured by a high-temperature isoperibolic calorimetry at T = (1750 ± 5) K. The measurements have been performed on alloys of five compositions x Ga: x Si = 0.15:0.85, 0.3:0.7, 0.5:0.5, 0.75:0.25 and 0.9:0.1. It has been determined that gadolinium is mixed with (Ga–Gd–Si) alloys with a significant heat evolution. Plots of concentration dependence of { Δ mix H ¯ Gd / ( 1 - x Gd ) 2 } for compositions x Ga: x Si = 0.15:0.85, 0.3:0.7, 0.5:0.5 and 0.75:0.25 at 0.24 < x Gd < 0.44 show sharp inflections. The inflection points correspond to transition of the liquid alloys into the heterogeneous state and can be used for liquidus surface determination. The integral enthalpy of mixing (Δ mix H) was calculated from the experimental Δ mix H ¯ Gd by Darken’s equation. For the six geometric models applied, the Toop model results are the best when compared with the experimental Δ mix H data. Two different methods were applied to extrapolate experimental Δ mix H into the area of overcooled liquid alloys. The Δ mix H values determined by both methods coincide well for the concentrations studied and for the area of extrapolation. The liquid ternary (gallium–gadolinium–silicon) alloys are characterized by significant negative Δ mix H up to −87.93 kJ · mol −1. The significant negative deviations from the geometric model (up to −13.33 kJ · mol −1) testify about chemical short-range ordering of ternary compound type, possibly associated with the existence of ternary compounds in the (Ga–Gd–Si) system.

Thermodynamic Properties of Si - Mn - Y System Alloys

High-temperature isoperibolic calorimetry has been used to measure the partial enthalpies of mixing for yttrium in the Si - Mn - Y ternary system at 1775 K along sections with various atomic ratios of silicon to manganese (0.85/0.15; 0.7/0.3; 0.6/0.4; 0.5/0.5; 0.3/0.7) for yttrium concentrations in the range 0 < xY < 0.4 together with the partial molar enthalpies of manganese for xSi/xY = 0.8/0.2. The integral enthalpies of mixing have been calculated from the partial ones for yttrium by Darken’s method. The addition of yttrium to the Si - M binary system to give the ternary Si - Mn - Y system increases the exothermic effects of the alloying substantially. There is a substantial effect on the thermodynamic parameters of the ternary alloys from the atomic interactions in the Si - Y and Si - Mn binary systems.

High temperature calorimetric study of liquid (gallium–gadolinium–germanium) alloys

(Gallium–gadolinium–germanium) liquid alloys have been studied by a high-temperature isoperibolic calorimetry at ( T = 1760 ± 5) K. The measurements have been performed along five sections with x Ge: x Ga = 0.15:0.85, 0.3:0.7, 0.5:0.5, 0.7:0.3 and 0.85:0.15 for 0.0 ⩽ x Gd ⩽ 0.55. It has been determined that Gd mixes with the ternary alloys with significant heat evolution. The partial enthalpy of mixing of gadolinium ( Δ mix H ¯ Gd ) reaches negative extreme at x Gd = 0.1 for each studied section. The Δ mix H ¯ Gd values for the x Ge: x Ga = 0.7:0.3 and 0.85:0.15 sections at x Gd = 0.45 sharply tends to zero that can be evidence of transition to heterogeneous area. The integral enthalpy of mixing (Δ mix H) was calculated from the experimental Δ mix H ¯ Gd by the Darken’s equation and independently from literature data on the boundaries using five geometric models. The Bonnier model shows the best agreement with the experimental data. The difference (ΔΔ mix H) between experimental and calculated by the model Δ mix H values was fitted through a polynomial dependence on x Ga and x Gd. The integral enthalpy of mixing in the ternary system was represented by sum of the Δ mix H calculated by the Bonnier model and the polynomial dependence of ΔΔ mix H. The extreme of the ΔΔ mix H term is −5.9 kJ · mol −1 at x Gd = 0.52 and x Ga = 0.24, which is about 7% of the experimental Δ mix H. It has been stated that the thermodynamics of the liquid (Ga–Gd–Ge) alloys is predominately determined by component interaction in the boundary (Ge–Gd) and (Ga–Gd) systems.

Calorimetric study of liquid gadolinium-based alloys

The enthalpies of mixing of liquid Gd-Si (1770±5 K) and Al-Gd (1760±5 K) alloys have been measured by high-temperature isoperibolic calorimetry. The calorimetric study of the gadolinium-based liquid alloys demonstrates the great negative enthalpies of mixing, which is associated with the contribution of GdSi and GdAl2 intermetallides into the liquid-state thermodynamics. The comparison of obtained results with literature data has been performed.

Thermodynamics of liquid aluminium–copper–silicon alloys

In this paper, thermodynamic properties of liquid Al–Cu–Si alloys were studied by electromotive force method with liquid electrolyte at 920–1250 K and by high-temperature isoperibolic calorimetry at 1750±5 K. The integral enthalpy of mixing in ternary Al–Cu–Si melts was estimated by Bonnier model for definition of boundary binary systems contribution to ternary alloys thermodynamics. The satisfactory agreement between experimental and estimated data demonstrates that thermodynamic properties of ternary liquid alloys are mainly defined by thermodynamic behaviour of boundary binary systems. Analysis of concentration and thermal dependencies of thermodynamic functions of mixing in liquid Al–Cu–Si alloys has been performed. It has been established that increasing of temperature results in decreasing of the integral enthalpy of mixing. This fact is probably associated with contribution of silicon clusters into ternary alloys thermodynamics.

Thermodynamics of liquid aluminium–copper–silicon alloys

In this paper, thermodynamic properties of liquid Al–Cu–Si alloys were studied by electromotive force method with liquid electrolyte at 920–1250 K and by high-temperature isoperibolic calorimetry at 1750±5 K. The integral enthalpy of mixing in ternary Al–Cu–Si melts was estimated by Bonnier model for definition of boundary binary systems contribution to ternary alloys thermodynamics. The satisfactory agreement between experimental and estimated data demonstrates that thermodynamic properties of ternary liquid alloys are mainly defined by thermodynamic behaviour of boundary binary systems. Analysis of concentration and thermal dependencies of thermodynamic functions of mixing in liquid Al–Cu–Si alloys has been performed. It has been established that increasing of temperature results in decreasing of the integral enthalpy of mixing. This fact is probably associated with contribution of silicon clusters into ternary alloys thermodynamics.

Thermodynamic properties of liquid Si–Ga–Y ternary alloys

The mixing enthalpies of Si–Ga–Y ternary melts have been determined using high-temperature isoperibolic calorimetry at 1750K. The formation of these melts is accompanied by large exothermic heat effects. The thermodynamic behavior of Si–Ga–Y liquid alloys and the phase equilibria in the solid state have been compared. The thermodynamic properties of Si–Ga–Y melts were modeled by a regular associated solution theory, and Gibbs free energies of alloy formation have been evaluated. The liquid Si–Ga–Y alloys are characterized by well-developed short-range order of chemical compound type.

Thermodynamics of liquid aluminium–copper–germanium alloys

Partial for aluminium and integral enthalpies of mixing of liquid Al–Cu–Ge alloys have been measured by high-temperature isoperibolic calorimetry at T=(1380±5) K. Thermodynamic activities, partial for aluminium and integral Gibbs free energies of mixing have been determined by the electromotive force method (emf) over the range 1050⩽ T/K⩽1250. Integral excess entropies of mixing have been calculated from calorimetric enthalpies and emf measured Gibbs free energies of mixing. The integral enthalpies of mixing and the integral excess Gibbs free energies of mixing have been also evaluated based on the literature data for boundaries using the Bonnier geometric model. Differences between experimental and calculated thermodynamic functions of mixing are positive. These facts as well as negative excess integral entropies of mixing reveal information about microsegregation in the melt. Therefore, the existence of ternary eutectic has been forecasted for Al–Cu–Ge phase diagram.

Calorimetric Investigation Of Liquid Gallium-Based Alloys

In this work, enthalpies of mixing of binary liquid gallium-gadolinuim and gallium-silicon alloys have been measured by high-temperature isoperibolic calorimetry at 1760±5 K. Significant negative enthalpies of mixing have been found for Ga -Gd system, while these values are positive for Ga - Si melts.

Enthalpy of mixing in liquid Al–Fe–Si alloys at 1750 K

The partial for aluminium and integral enthalpies of mixing in liquid Al–Fe–Si alloys have been measured by high-temperature isoperibolic calorimetry at 1750±5 K. The study has been performed along five sections with constant concentration ratios of Si and Fe. The integral enthalpies of mixing were simulated according Bonnier geometry. The differences between experimental and simulated data possess negative values within the experimental errors range, which may testify that ternary interaction is negligibly small at the experimental temperature.