Dissolution Of Laves Phase Research Articles

Microstructure Evolution and Homogenization Kinetics of 15Cr–30Ni–Fe Heat‐Resistant Alloy

The as‐cast microstructure, microsegregation of alloying elements, and microstructure evolution during homogenization of the newly designed 15Cr–30Ni–Fe heat‐resistant alloy are studied. Ti, Nb, Si, and Mo segregate at the interdendritic region. The brittle eutectic Laves phase contains Fe, Ti, Ni, Nb, Si, and Mo, which is identified as the Fe2Ti Laves phase. The activation energy for the Fe2Ti Laves phase dissolution is close to the activation energy for Ti diffusion in the γ matrix based on the Johnson–Mehl–Avrami–Kolmogorov analysis. The back‐diffusion of Ti to the γ matrix is the limiting step for the dissolution of Fe2Ti Laves phase. The kinetic equation of homogenization considering lattice parameters and pre‐exponential factor correction is established. After the double‐stage homogenization at 980 °C/10 h + 1140 °C/4 h, the volume fraction of the Laves phase decreases from 5.11% to 0.26%, and the large eutectic Laves phase is completely dissolved. The reduction in the standard deviation of microhardness at different soaking times effectively reflects the gradual decrease in the degree of microsegregation of alloying elements. The average grain size of the alloy after homogenization is 410 ± 63.1 μm, which is beneficial to control the further refinement of grain during the subsequent hot working.

Evolution of Laves phase related to tensile properties in cast ATI 718Plus under pulsed electric current

The Laves phase will seriously deteriorate the subsequent hot working and welding performance of cast ATI 718Plus. In traditional homogenization annealing, two-stage treatment is used to prevent the formation of harmful eutectic structures due to the initial melting of the low-melting point Laves phase. This has several obvious disadvantages including high processing temperature, long processing time and complicated operation. Electrical pulsed treatment, as a new efficient, feasible and energy-saving green means, has rapidly achieved the dissolution of Laves phase. The increase in diffusion rate of Nb element in Ni matrix by pulsed electric current is due to the enhancement of defect migration and vacancy defect density, leading to a significant enhancement in the diffusion kinetics and accelerating the dissolution of Laves phase. Laves phase dissolution process under the pulsed electric current is from the aggregated state accompanied by dense needle like η phase to the discrete state accompanied by sparse needle like η phase, finally forming a single long strip and being dissolved into an intermittent state until it disappears. In all, using pulsed electric current instead of traditional heat treatment for annealing cast ingots has the potential to achieve one-step homogenization, completely dissolving the Laves phase while eliminating element segregation.

Investigation of Laves Phase Dissolution and Homogenization Kinetics in IN718 with 0.4 Wt.% Si Through a Combination of Characterization and Calculations

Investigation of Laves Phase Dissolution and Homogenization Kinetics in IN718 with 0.4 Wt.% Si Through a Combination of Characterization and Calculations

Effects of Laves phase precipitation embrittlement and its dissolution kinetics in super-ferritic stainless steels on the ductile-brittle transition

This study simulated the Laves phase precipitation embrittlement of super-ferritic stainless steels (SFSSs). The dissolution kinetics of the Laves phase, grain coarsening, and their effects on the mechanical properties and ductile-brittle transition during dissolution heat treatment were subsequently studied. The Laves phase dissolution adhered to the Johnson-Mehl-Avram-Kolmogorov variation expression, exhibiting an activation energy of approximately 368 kJ mol−1. High-temperature reheating (1100 °C) resulted in severe grain coarsening, leading to brittle fracture. A dissolution treatment of only 0.5 h at 1050 °C resulted in a high yield strength of 407.8 MPa, large elongation of 29.6%, and impact toughness of 237.2 J/cm2 because the entirety of the Laves phase was dissolved and no obvious grain growth was observed. This indicates that dissolution heat treatment is a simple and feasible method for recovering the ductility and toughness of Laves phase precipitation-embrittled SFSSs.

Atomic insights into the preferential dissolution of Laves phase of 9% Cr heat resistant steels in the strong alkaline solution

Two types of 9% Cr heat resistant steels were used to investigate the preferential dissolution mechanism of Laves phase in 8 mol/L NaOH solutions in an atomic scale by quasi-in-situ TEM analyses and first principles calculations. The dissolution of Laves phase is due to the unprotective oxide film. The dissolution rate of Laves phase was associated with the crystal orientation, and the stacking faults hinder the dissolution of Laves phase in a strong alkaline solution. Further, DFT calculations were used to illustrate the dissolution process of Laves phase, and the result is consistent with the TEM observation.

Enhanced strength of additively manufactured Inconel 718 by means of a simplified heat treatment strategy

This study simplified the heat treatment route and reduced the post-processing burden for laser powder bed fusion IN718 (a nickel-based superalloy). The tailored route retained advantageous microstructures and improved tensile strength when compared to the conventional post-processing strategy. The implementation of a single pre-aging step (combining the stress relief, HIP, and solution steps into one) and a single-step aging treatment (as opposed to two-step aging) resulted in a total heat treatment time of 15 h, which is far shorter than the conventional five-step strategy (42 h). The grain structure, pore structure, and room-temperature tensile properties were measured for three material conditions: the as-built condition, the baseline condition (a conventional five-step heat treatment route), and the HIP1020RQSA condition (novel high pressure rapid quenching HIP treatment followed by a single-step age). In the HIP1020RQSA condition, the high pressure (200 MPa), short hold time at a carefully selected temperature (0.5 h at 1020 °C), and rapid quenching (2150 °C/min) were implemented. Unique findings in the microstructure include generation of localized micro-scale recrystallization throughout the retained columnar grain and sub-grain structures, internal pore closure with a shortened HIP soak time, incomplete dissolution of Laves phase, and the absence of δ phase. The single step aging treatment also generated γ′ and γ′′ precipitates. The HIP1020RQSA treatment improved the yield strength of the baseline condition from 1112 MPa to 1209 MPa, decreased total elongation from 24.9% to 23.2%, and still exceeds the minimum Z direction (build direction) tensile properties outlined in ASTM F3055–14a.

Achieving High Strength and Creep Resistance in Inconel 740H Superalloy through Wire-Arc Additive Manufacturing and Thermodynamic-Guided Heat Treatment.

Inconel 740H superalloy is commonly used in advanced ultra-supercritical power plants since it possesses excellent strength and creep resistance. This study investigates the microstructure and mechanical properties of Inconel 740H superalloy fabricated using wire-arc additive manufacturing. The as-printed microstructure consisted of columnar γ grains with the Laves phase and (Nb, Ti)C carbides as secondary phases. The anisotropy in grain structure increased from the bottom to the top regions, while the hardness was highest in the middle portion of the build. To guide the post-heat treatment design, thermodynamic and kinetic simulations were employed to predict the temperature and time. Complete recrystallization with the Laves phase dissolution occurred throughout the build after homogenization at 1200 °C for 2 h. The peak hardness was achieved after aging at 760 °C for 12 h with the M23C6 carbides decorating the grain boundaries and γ' precipitates in the grain interior. The yield strength (655 MPa) and ductility (29.5%) in the post-heat treated condition exceeded the design targets (620 MPa, 20%). Stress rupture tests at 750 °C showed that the high-temperature performance was at par with the wrought counterparts. The fracture mode after rupture was identified to be intergranular with the presence of grain boundary cavities along with grain boundary sliding.

Structure and Properties Evolution of AZhK Superalloy Prepared by Laser Powder Bed Fusion Combined with Hot Isostatic Pressing and Heat Treatment

The structure and properties of samples obtained by the laser powder bed fusion (LPBF) method from the AZhK alloy, intended for the manufacture of heavily loaded body parts with operating temperatures up to 800 °C, have been studied. The optimal mode of LPBF, ensuring the attainment of the minimal residual porosity of 0.02%, was identified for the superalloy AZhK. Additionally, the evolution of the microstructure of LPBF samples after hot isostatic pressing (HIP) and heat treatment (HT) was studied using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The macrostructure of LPBF samples is represented by columnar grains oriented in the direction of predominant heat dissipation, perpendicular to the build plate. At the microlevel, the structure consists of colonies of columnar dendrites. Nb4AlC3 and Nb6C4 carbides, as well as the Mo2Hf Laves phase, are precipitated in the interdendritic region as a result of doping element segregation. The low strength of the LPBF samples (σ = 967 ± 10 MPa) is caused by the fact that there are no reinforcing particles and by high internal stress due to high crystallization speed. HIP and HT were found to have a favorable effect on the structure and properties of the LPBF samples. The post-treatment resulted in uniform distribution of γ′-phase precipitates sized up to 250 nm in the matrix bulk and carbides at grain boundaries, as well as Laves phase dissolution. Therefore, the strength characteristics were significantly improved: by 45% at room temperature and by 50% at elevated temperatures. High strength and ductility were attained (at 20 °C, σ20 = 1396 ± 22 MPa and δ = 19.0 ± 3.0 %; at 650 °C, σ650 = 1240 ± 25 MPa and δ = 15.8 ± 1.5%; at 750 °C, σ750 = 1085 ± 23 MPa and δ = 9.1 ± 2.3%). An ejector-type part was fabricated, and its geometric parameters coincided with those in the electronic models. After conducting computed tomography, it was found that there are no defects in the form of non-fusion and microcracks within the volume of the part; however, it was observed that the pore size is ≥20 μm.

Dissolution kinetics of Laves phase during homogenization heat treatment of additively manufactured Inconel 718 superalloy

The Laves phase in the as-built Inconel 718 (IN718) superalloy is known as undesirable phase, which limits the industrial applications of the manufactured parts. Post-processing in the form of the homogenization heat treatment is known as an effective method to eliminate the deleterious Laves phase, where understanding its dissolution kinetics is crucial for optimization of the heat treatment schedule. Accordingly, the IN718 nickel-based superalloy manufactured by the laser powder bed fusion (LPBF), also known as selective laser melting (SLM), was homogenized at temperatures from 950 to 1150 °C for 30 to 120 s, and the Laves phase dissolution was studied by microstructural analysis, its kinetics was modeled by Johnson-Mehl-Avrami-Kolmogorov (JMAK) analysis, and the model was validated by the second Fick's law. The activation energy for Laves phase dissolution was determined as ∼160 kJ/mol with an Avrami exponent of ∼1, which was attributed to the high dislocation density and fine microstructure of the LPBF material, and accordingly, the lattice and grain boundary diffusion of Nb in Ni were characterized as the underlying atomistic mechanisms during the dissolution of the Laves phase. These findings are based on the underlying atomistic mechanisms, which can shed light on the principles of dissolution kinetics of Laves phase in IN718 for additive manufactured parts. Moreover, the conducted comparison among LPBF, directed energy deposition (DED), and conventional casting indicated that the fabricating method and the initial segregation play key roles. In other words, due to its lower segregation degree, LPBF has faster Laves phase dissolution kinetics in comparison with other fabrication methods.

Microstructure evolution and strengthening mechanism of γ′-strengthening superalloy prepared by laser powder bed fusion

Recently, γ′ phase has been introduced into the solid-solution strengthening Haynes 230 alloy to improve alloy strength for better satisfying the rigorous service environment. However, previous research shows that γ′ phase was not precipitated under the as-fabricated condition and harmful Laves phases with high-W content, which have never been reported, appeared in the novel alloy. Therefore, in this study, Laves phase dissolution mechanisms during solution heat treatments (SHT) and γ′ strengthening mechanism after subsequent aging heat treatment (AHT) of a novel γ′-strengthening superalloy prepared by laser powder bed fusion (LPBF) were first investigated. The results show that Laves phases continue to dissolve with the increment of SHT temperature and finally disappear after SHT-ed at 1200 °C. The higher dissolution difficulty of Laves phases is closely related to the lower diffusion coefficient of W element. The long-range diffusion of solute atoms mainly controls the dissolution of Laves phases in the early homogenization stage. As the holding time increases, the γ/Laves interface widths for the solute atoms diffusion decrease and thus the dissolution process is gradually governed by the interface reaction in the later stage. After AHT, numerous nanosized γ′ particles are precipitated. With increasing SHT temperature, the ultimate tensile strength (UTS) and yield strength (YS) of the AHT-ed samples decrease while the elongation (EL) increases, which is mainly caused by the Laves phases dissolution and grain recrystallization. The 1200+AHT sample presents an excellent combination of strength and ductility with UTS of 1467.7 MPa, YS of 1244.6 MPa and EL of 6.3%. The dominant strengthening contributions in the AHT-ed samples are γ′ strengthening and solution strengthening.

As-cast microstructure and homogenization kinetics of a typical hard-to-deform Ni-base superalloy

In this paper, the as-cast microstructure, microsegregation, and the kinetics of (γ+γ′) eutectic phase and Laves phase dissolution in GH4151 alloy were studied by the optical microscope (OM), scanning electron microscope (SEM), electron probe microanalysis (EPMA), differential scanning calorimetry (DSC), and high-temperature water quenching text. The results show that W and Al elements are segregated into the dendrites arm, while Mo, Nb, and Ti are segregated into the interdendritic region. The initial melting point temperature of the MB2 phase was near 1100 °C, the redissolution temperature range of γ′ phase is 1130–1160 °C, the obvious dissolution temperature of Laves phase was above 1145 °C and the γ + γ′ eutectic phase was redissolved obviously above 1165 °C. Based on the JMAK analysis, the activation energies of dissolution of Laves phase (266.3 kJ/mol) and γ+γ′ phase (279.5 kJ/mol) are close to the activation energy for the diffusion of Mo in Ni (288.15 kJ/mol) and Ti in Ni (288.15 kJ/mol), respectively. The back-diffusion of Mo and Ti into austenite is controlling the micro-mechanism for the dissolution of Laves phase and (γ+γ′) eutectic phase, respectively.

The influence of solution temperature on microstructure evolution and mechanical properties of ATI 718Plus repaired by wire and arc additive manufacturing

Wire and arc additive manufacturing technology was applied to repair damaged 718Plus components to save life-cycle costs. In this work, the effects of different solution temperatures on the microstructural evolution and tensile properties of repaired samples were investigated in detail. The results showed that the heat-treated microstructure in the deposited zone (DZ) mainly consisted of columnar grains along the building direction. Laves phase, needle-like η phase and γ′ phase were gathered in the interdendritic region. In contrast, the microstructure of the substrate zone (SZ) contained equiaxed grains with grain boundary (GB) η phase and a uniform distribution of γ′ phase. With the solution temperature increasing, the undesirable Laves phase was gradually dissolved, and its morphology varied from long-striped to granular. The number of η phases was observed to increase initially and then decrease with morphology changing to granular. The resultant granular η phase in SZ lost its pinning effect on GBs, leading to the rapid coarsening of grains in SZ. Tensile tests show that the dissolution of Laves phase and η phase in DZ helps to improve the ductility while the grain growth results in the decrease of tensile stress.

The formation and dissolution mechanisms of Laves phase in Inconel 718 fabricated by selective laser melting compared to directed energy deposition and cast

In this study, we explain why the amount of Laves phase in Inconel 718(IN718) manufactured by selective laser melting (SLM) unexpectedly increases under extremely rapid solidification and clarify its distinct dissolution behavior during heat treatment based on a comparative analysis of laser directed energy deposition (L-DED)-built and cast IN718. Compared with the cast and L-DED, SLM has much higher cooling rate, which greatly improves the dendrite growth rate and the solute trapping during the solidification process of molten pool. Thus, more Nb atoms are trapped in the matrix, and less Nb atoms are expelled to form inter-dendritic Laves phase in SLM-built IN718. However, the volume fraction of Laves phase is the highest in SLM-built IN718, which is attributed to the lower Nb concentration in the Laves phase and few Nb-rich region. During homogenization treatment, the dissolution of Laves phase is controlled by three-dimensional diffusion process at the early stage, and then is mainly controlled by the interface reaction process. After homogenization, there are still many tiny carbides, oxides, and nitrides undissolved both along the grain boundaries and inside the grains.

On the detailed morphological and chemical evolution of phases during laser powder bed fusion and common post-processing heat treatments of IN718

IN718 is the most common Ni-based superalloy for manufacturing aircraft engine parts via thermo-mechanical treatments. The evolution of nanoscale strengthening phases is well researched, enabling optimization of strength, fatigue, and creep properties. Recently, IN718 has shown great viability for laser powder bed fusion (LPBF) additive manufacturing of aerospace parts. However, the detailed microstructure-property relationships during thermal profiles typical to LPBF are not yet well understood. Previous works reported interdendritic precipitation of Laves phase. These detrimental particles can be dissolved by heat treatments, however, the detailed nanoscale phase evolution remains unknown. Using atom probe microscopy, we report on the detailed morphological and chemical evolution of phases in IN718 after LPBF with chessboard versus meander scanning strategies, and direct ageing versus homogenization and ageing treatments. Due to differences in scanning vector length, up to 3.6 times larger dendritic structures, double volume fractions of Laves particles, and Al clusters are found in the chessboard strategy. Coarser matrix grains and a higher dislocation density are detected in the meander strategy. The precise chemical composition and morphology evolution of the matrix, Laves, MC, γ′, and γ′′ phases are obtained and correlated to hardness. Retained Laves phase after direct ageing causes precipitation of 4% volume fraction of γ′′, with additional coarsened precipitates formed along dislocations. Direct ageing leads to an increase in hardness corresponding to roughly 190 HV. Due to Laves phase dissolution, a volume fraction of 16% of compositionally stable, larger γ′′ precipitates is found after homogenization and ageing, also causing partial matrix recrystallization.

Effect of treatment mode on microstructure evolution and mechanical properties of nickel-based superalloy fabricated by selective laser melting

Combined with scanning electron microscopy, transmission electron microscope, X-ray diffraction and electron backscatter diffraction, the effects of three treatment modes consisting of as-deposited, solid solution and solution aging state on mechanical structure-properties of a nickel-based superalloy fabricated by selective laser melting were studied. Grains have preferred orientation, i.e. strong texture along {100}. The phase transformation processes during post-heat treatments include dissolution of Laves phase, precipitation of strengthening phases γ′, γ′′ and δ, and size reduction of δ phase. Especially for solution aging treatment, the refined grains, high dislocation density and added high-angle grain boundaries cause a significant increase in strength and a decrease in ductility, which is consistent with the results of the tensile tests. The interior cracking behavior related to the micro-voids and microcracks formed by dislocation pile-ups and uncoordinated deformation around harder δ phase in a vacuum environment becomes a typical ductile failure mode.

Incipient melting phase and its dissolution kinetics for a new superalloy

Abstract Based on XRD, SEM and EDS analyses, the phases in GH4151 alloy were identified. Differential scanning calorimetry (DSC) experiment and metallographic method were carried out to determine the incipient melting temperature (IMT) of the alloy. The result shows that the IMT of alloy is situated between 1150 and 1160 °C. Subsequently, the dissolution process of Laves phase was carried out, and the dissolution kinetic equations were obtained at different temperatures. And then based on the verification of experiments, the model was confirmed to be credible to predict the fraction of the Laves phase dissolution. Finally, the results of diffusion coefficients indicate that the diffusion of Nb element is a critical factor for homogenization process of GH4151 alloy.

Microstructure and Fatigue Crack Growth Behavior of Inconel 718 Superalloy Fabricated Via Laser Directed Energy Deposition Additive Manufacturing

This work investigated the microstructure and its influence on room-temperature fatigue crack growth (FCG) behavior of Inconel 718 (IN718) alloy fabricated with laser-based directed energy deposition (L-DED). As-deposited specimens were heat-treated by direct aging (DA), solution treatment + aging (SA) and homogenization + solution treatment + aging (HSA) respectively to investigate the effect of post-heat-treatment. On comparison with as-deposited microstructure, which mainly consists of γ dendrite and Laves phases in the interdendritic regions. Dendritic segregation still appears after DA heat-treatment, which is certified to alter the precipitation kinetics of γ′′/γ′ precipitations of IN718 and induce the formation of more abundant γ′′/γ′ precipitations in interdendritic Nb-rich regions versus the dendritic trunk regions. After SA heat-treatment, Nb released from the dissolution of Laves phase is prone to diffuse to the ambient interdendritic regions, which facilitates the formation of δ-phase and the homogeneous precipitations of γ′′/γ′ phases in dendritic trunk region. After HSA heat-treatment, the Laves phases are eliminated completely, the dispersive γ′′/γ′ precipitates (~30 nm) are distributed within the bimodal recrystallized grains. The results of FCG testing reveal that as-deposited specimen possesses the lowest threshold for fatigue-crack initiation (ΔKth) and the highest FCG rate (FCGR). The ΔKth and FCGR of DA specimen do not have the notable improvement versus those of as-deposited specimen, due to its inferior strength-plasticity mainly caused by heterogeneous γ′′/γ′ phases and Laves particles. The fatigue-crack propagates easily along the precipitate-free zone around short-acicular δ-phase, which causes the crack branching and deflection, enhances the resistance to FCG of SA specimen to some extent. The ΔKth of HSA specimen increases by ~2.6 times compared with as-deposited specimen and reaches 10.8 MPa∙m1/2, due to its decent strength-plasticity (~1130 MPa, ~26.5%). Especially, the ΔKth and FCGR of HSA specimen are comparable to that of the wrought IN718. The FCG behaviors of all specimens predominantly occur in the transgranular ductile fracture mode. Overall, the present study demonstrates that a judicious post-heat-treatment can enhance the damage tolerance of L-DED IN718 by increasing ΔKth and decreasing FCGR.

Influence of Homogenization and Solution Treatments Time on the Microstructure and Hardness of Inconel 718 Fabricated by Laser Powder Bed Fusion Process.

In the present study, Inconel 718 (IN718) superalloy fabricated by laser powder bed fusion (LPBF) has been characterized focusing on the effect of both homogenization and solution treatment time on grains structure, crystallographic texture, precipitates formation/dissolution and material hardness. For this purpose, a heat-treatment time window with a wide range of soaking times for both treatments was established aiming to develop the optimal post-treatment conditions for laser powder bed fused IN718. It was found that the as-printed IN718 is characterized by very fine columnar/cellular dendrites with Laves phase precipitating at the grain boundaries as well as inter-dendritic regions, which differs from the microstructure of wrought and cast materials and requires special heat-treatment conditions different from the standard treatments. The results reveal that the relatively short homogenization treatment at 1080 °C for 1 h was not enough to significantly change the as-printed grain structure and completely dissolve the segregates and Laves phase. However, a completely recrystallized IN718 material and more Laves phase dissolution were obtained after homogenization treatment for 4 h. A further increase in time of the homogenization treatment (7 h) resulted in grain growth and coarsening of carbides precipitates. The solution treatment time at 980 °C did not cause noticeable changes in the crystallographic texture and grain structure. Nevertheless, the amount of δ-phase precipitation was significantly affected by the solution treatment time. After applying the heat-treatment time window, the hardness increased by 51–72% of the as-printed condition depending on the treatment time due to the formation of γ′ and γ″ in the γ-matrix. The highest material hardness was obtained after 1 h homogenization, whereas the prolonged time treatments reduced the hardness. This study provides a comprehensive investigation of the post heat-treatments of the laser powder bed fused IN718 that can result in an optimized microstructure and mechanical behavior for particular applications.

Enhancing mechanical properties of quasi-continuous-wave laser additive manufactured Inconel 718 through controlling the niobium-rich precipitates

Controlling of Nb-rich intermetallics is an important topic for laser additive manufacturing (LAM) of Inconel 718. In the present work, a novel quasi-continuous-wave LAM (QCW-LAM) with different pulse frequencies is used to control the morphology, distribution and amount of Nb-rich phases of Inconel 718. The results show that dispersively distributed Nb-rich Laves phases are produced by introducing equiaxed dendrites at a low pulse frequency while a high pulse frequency results in coarse and chain-like Laves phases. The samples featured by fine and discrete Laves phases show a good response to the post solution-aging treatment in which the dissolution of Laves-phase and subsequently discrete precipitations of δ-phase as well as high-density precipitation of γ″-Ni3Nb strengthening phase are promoted. Thus, a good combination of strength and ductility is achieved for the QCW-LAM fabricated Inconel 718. This study shows a desired mechanical property can be obtained by synergistically optimizing the microstructures in which various Nb-rich phases are involved even though the formation of brittle Laves phases is hardly avoided during LAM of Inconel 718.

Dissolution of laves phase by re-austenitization and tempering of creep strength enhanced ferritic steel

ABSTRACTFormation of Laves phase in creep strength enhanced ferritic steel is investigated using re-austenitization and tempering treatment. The as-received material is exposed to 620°C for 4560 h aging, and then re-austenitizated at 1050°C for 1 h, and followed by tempering at 760°C for different times (2 and 4 h). After re-austenitization and tempering, the dissolution of Laves phase is observed while grain size and microhardness have not changed significantly. A model is suggested to quantify the dissolution of W-containing Laves phase. Thermo-Calc is used to predict driving forces for precipitation of Laves and M23C6 phases.