Intermetallic Diffusion Research Articles

The relationship between inter-diffusion and self-diffusion of different liquid metals studied by molecular dynamics simulations

Long-capillary simulation method was used to calculate the inter-diffusion coefficient using nonequilibrium molecular dynamics simulations. The inter-diffusion coefficient of the binary Al80Ni20, Al80Cu20, La80Ni20 and La80Al20 melts were calculated over a wide temperature range. We found that the relationship between inter- and self-diffusion coefficients of Al80Cu20 melts can be well expressed by Darken equation, which agreed with the previous results. For Al80Ni20, La80Ni20 and La80Al20 melts, dynamic cross correlation factor S was needed to correlate the Darken equation. S of Al80Ni20 and La80Ni20 ranged from 0.68 to 0.92, while that of La80Al20 was larger than 1. The effect of pressure on S was further investigated. We found that S of Al80Ni20 under 30 GPa was about 0.46 at 2000K and it was much lower than that of zero pressure, which means that the pressure had a great influence on S. Our investigations provided an improved understanding of cross correlation factor S.

Three-point bending study on the microscopic fracture behavior of pre-oxidized Cr-coated Zr-4 alloys

In this study, an in situ three-point bending test was carried out to study the mechanical properties and cracking behavior of the Cr-coated Zr-4 alloy considering the effect of pre-oxidation. The results showed that high temperature pre-oxidation led to the formation of intermetallic ZrCr2 at the coating/substrate interface and an α-Zr(O) layer beneath the interface. During the three-point bending test, the Cr coating and Zr-4 substrate showed good plastic deformation. However, the brittle intermetallic ZrCr2 diffusion layer exhibited cracks in the early stage, which accelerated the crack penetration to the Cr coating and the Zr-4 substrate, leading to the pre-failure of the pre-oxidized sample.

Study of the interfacial reactions controlling the spreading of Al on Ni

Despite the importance in high-temperature processing, wettability studies focusing on liquid aluminum (Al) on solid nickel (Ni) at high temperatures are scarce due to the difficulty of performing experiments and the complexity of interfacial physical and chemical activities. The effects of interrelated multi-factors, including intermetallic compounds (IMCs) formation and diffusion on wetting dynamics is still debatable. Therefore, in this study, we investigated the reactive spreading of liquid Al on solid Ni by using the combined pendant/sessile drop method between 750 and 950 °C. The effects of Ni dissolution into Al on the spreading dynamics were limited due to the low Ni solubility below 950 °C. Two continuous Al-rich IMC layers, Al3Ni and Al3Ni2 layers formed at the Al/Ni interface during the isothermal holding stage and affect the final wetting behavior. Additional capillary quenching experiments confirmed that the Al3Ni phase was the first formed phase. At equilibrium, the Al3Ni layer was pinned at the triple-phase line at 750 °C while it can spread ahead of the liquid front at higher temperatures. This process may be the main reason why at higher temperatures a better spreading is observed as the Al3Ni layer has a larger affinity to Al than the pure Ni substrate.

Influence of Nb on Ti diffusion in γ-TiAl intermetallics studied by mechanical spectroscopy

The development of intermetallic titanium aluminides has been driven by the aeronautic and aerospace industries because of the excellent mechanical properties and low density of γ-TiAl based alloys. Up to now, several generations of γ-TiAl based alloys were developed with increasing complexity of the alloy systems. Nb is one of the most important alloying elements in γ-TiAl alloys and although it is considered as a slow diffuser, its influence has not been fully quantified yet. In this work we demonstrate, through mechanical spectroscopy measurements conducted on several γ-TiAl based alloys with different Nb content, that Nb impedes the diffusion of Ti atoms in the α2-Ti3Al phase. Internal friction measurements show a relaxation peak P(α2), which is associated with short distance diffusion of Ti atoms in the α2 phase, involving stress-induced rotation of dipoles Al-VTi-Al, whose activation energy is dependent on the Nb content. The increase of the activation energy is quantified as ΔEa(Ti)= 0.037 eV × at% Nb, being attributed to the next-neighbor interaction of Nb atoms with the local configuration of Ti-VTi. This mechanism also produces a further broadening of the relaxation peak, which is attributed to the near-next-neighbor interactions for high Nb contents. Finally, an atomic model for the mechanism responsible for this relaxation is proposed allowing to explain the observed experimental behavior.

Surface effects on deuterium permeation through vanadium membranes

Dense vanadium-based membranes offer high permeability and perfect selectivity to hydrogen isotopes, maintain favorable neutronic properties, and are compatible with liquid metals such as PbLi. These properties make vanadium membranes a promising fusion fuel cycle technology for processes such as tritium extraction from PbLi and exhaust processing. Surface contamination has a deleterious effect on the gas-phase hydrogen permeation through vanadium, and the reported permeabilities range from 10-14 to 10-7 mol m-1 s-1 Pa-0.5. Thin dense films of palladium applied to clean vanadium surfaces enable a consistently high hydrogen permeability. In this study, uncoated vanadium resulted in deuterium permeabilities ranging from 2.8 × 10-11 to 6.4 × 10-9 mol m-1 s-1 Pa-0.5 at 300 °C–700 °C, respectively. Post-test analysis revealed a VOx surface layer and VCx subsurface layer formed on the feed side, while the as-received surface oxide dissolved leaving a submonolayer oxide on the permeate surface. The Pd-coated V resulted in a maximum deuterium permeability of 2.1 × 10-7 mol m-1 s-1 Pa-0.5 at 375 °C upon activation of the Pd surface by oxidation and reduction. The deuterium permeation declined upon heating to 500 °C due to intermetallic diffusion between the Pd and V. The Mo2C-coated V resulted in deuterium permeabilities ranging from 2.7 × 10-10 to 1.8 × 10-9 at 500 °C–700 °C, respectively, and a post-test analysis found the carbon in the Mo2C layer had dissolved into the V near the interface.

Bronze Electroplating: Stability, Nucleation and Growth Study of a New Green Formulation

Bronze electroplating is a widely used process in the electronics and costume jewelry industrial sectors as an anti-corrosion coating and barrier layer against intermetallic diffusion. The study of this alloy is also essential for the realization of copper-zinc-tin sulfide (CZTS) compounds, a quaternary semiconductor with a growing interest for the realization of thin film photovoltaic devices. The galvanic baths currently on the market are alkaline with a high amount of sodium or potassium cyanide to complex the metal ions. Cyanide salts are extremely dangerous for their toxicity, blocking cellular respiration. For this reason, cyanides are considered a danger both for the environment as well as for the workers with whom it comes in contact. In this study, a new eco-friendly, acidic and cyanide-free formulation was developed for the deposition of the Cu-Sn alloy.To achieve this goal, methanesulfonic acid (MSA) was chosen as electrolyte, which is biodegradable as part of the natural sulfur cycle. Various recipes have been evaluated to obtain a solution that was stable over time and that did not lead to the precipitation or oxidation of its components. Copper sulphate, copper methanesulfonate and tin methanesulfonate solutions were used as precursors of the metals [1]. As stabilizing additives nitrilotriacetic acid (NTA) and 2-picolinic acid (2PA), complex agents for copper, and hydroquinone (HYD), antioxidant agent for tin, were evaluated. The composition of the films, obtained both by potentiostatic and galvanostatic deposition, were analyzed by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS) and, to investigate the structural phases of the deposits, XRD measurements were carried out. Finally, nucleation and growth as a function of the concentration of thiourea (TU) and potassium and sodium tartrate (PST), regulating additives for the deposition of copper and tin, respectively, were studied by chronoamperometric methods, in order to achieve progressive growth and therefore a lucid deposit. The present study funded by the PRIN Project (“Progetti di Ricerca di Rilevante Interesse Nazionale”), “Novel Multilayered and Micro-Machined Electrode Nano-Architectures for Electrocatalytic Applications (Fuel Cells and Electrolyzers)”, grant number 2017YH9MRK.

Dissimilar Metal Joining of Ti and Ni Using Ti-Al Powder Interlayer Via Rapid Thermal Explosion Method

To achieve the low energy consumption and high strength joining between Ti and Ni, a novel joining method (rapid thermal explosion, TE) was developed for joining dissimilar metals using Ti-Al mixture powders as flux. The TE reaction temperature of Ti-Al flux was measured, and the microstructure and mechanical properties of Ti/Ni joint were investigated. The results reveal that the combustion temperature of the Ti-Al powder interlayer is 1103 °C, which is higher than the joining temperature, and an obvious self-exothermic phenomenon lasts 20 s. The intermetallic compound diffusion layers formed at both interfaces mainly owing to the diffusion of Al and the growth activation energy of diffusion layers near both interfaces are 79.68 kJ/mol and 38.26 kJ/mol, respectively. Based on the sheer strength and diffusion layer, the formation mechanism of Ti/Ni joints is metallurgical bonding through atomic diffusion and formation of the diffusion layer.

Microstructure and Mechanical Properties of Ti-6Al-4V Alloy/Interstitial Free Steel Joint Diffusion Bonded with Application of Copper and Nickel Interlayers

The application of interlayers in solid-state diffusion bonding is considered for facilitating improved joint strength as well as optimizing the bonding parameters. In case of dissimilar metals, the interlayers are preferred to promote diffusivity by reducing the metallurgical incompatibility. In the present work, the effect of formation of intermetallics at interfaces of the dissimilar joints between Ti-6Al-4V (Ti64) alloy and interstitial free (IF) steel, produced by direct diffusion bonding as well as by using the interlayers of copper and nickel, was evaluated. The diffusion bonding experiments were performed in a temperature range of 1023 K to 1223 K, under a constant pressure of 10 MPa for 10 minutes, in high vacuum conditions. It was observed that diffusion of interlayer(s) into the base metals increased with bonding temperature, which led to the increase in intermetallic layers at the joint interface. At 1223 K, the influence of interlayer on microstructure of interfaces was reduced by complete diffusion of interlayers and subsequently led to the interdiffusion of base metals. The maximum shear strength of ~ 186 MPa was recorded for the bonding performed using a nickel interlayer at 1023 K. Detailed microstructure analysis, nanoindentation measurements and shear tests suggest that the presence of a thin layer of hard TiFe intermetallic at the interface has no adverse effect, but a soft remnant interlayer can deteriorate the shear properties of the diffusion-bonded joints.

3d-visualization of magnesium strengthening mechanisms for a description of experimentally obtained data of alloying effect in Mg-Ga system

Based on laws of theory of materials strengthening were discribed the experimentally obtained alloying effect in Mg-Ga system and shown using program for 3d atomic structures. As known from our experiments a homogeneous “wavy” microstructure of the diffusion zone forms as result of mass-transfer of molten gallium into the volume of magnesium alloys. SEM chemical composition shows Mg 65% wt. and Ga 35% wt. and X-ray spectra diffraction data - Mg5Ga2 intermetallic phase formation. Such intermetallic diffusion zone provides the significant strengthening effect of microstructure which was determined experimentally by the indentation method. The 3-d visualization shows the reaction and changing of an original crystal structure of magnesium atomic lattice upon diffusion doping with foreign atoms of gallium and then is shown the coalescence of Mg5Ga2 intermetallic crystal with crystals surfaces of Mg-matrix. So, investigated Mg-alloy strengthening at alloying with Ga explained by two main factors. At first is the formation of intermetallic phases with the ordering and consolidation of the crystal structure of the matrix by the ligature atoms, which is the key factor of the strengthening mechanism fixed experimentally. Second, when hexagonal and orthorhombic atomic structures growth according to their spatial type, a significant disorientation of structural fragments occurs, an increase in the density of the amorphous transition layer, a twinning of the structure in the interphase boundaries, which leads to the formation of intrinsic mutual deformation and a high level of internal stresses.

Preparation of High Stability Pd/Ceramic/Ti-Al Alloy Composite Membranes by Electroless Plating.

High stability Pd/ceramic/Ti-Al alloy composite membranes were prepared by electroless plating. Ceramic membranes fabricated by an in situ oxidation method were used as an inter-diffusion barrier between the Pd layer and the Ti-Al alloy support of the membranes to prevent intermetallic diffusion. The stabilities of the ceramic membranes at high temperatures in an H2 atmosphere were investigated. The permeation performances and stabilities of the Pd/ceramic/Ti-Al alloy composite membranes were also studied. The results showed that the thickness, pore size, and microstructure of the ceramic membranes did not change significantly after the treatment in an H2 atmosphere at high temperatures, indicating that the ceramic membranes prepared by the in situ oxidation method were stable in an H2 atmosphere at high temperatures. The thickness of the Pd layer was ~13 μm. The hydrogen permeability and H2/N2 selectivity of the Pd composite membranes at 773 K were 2.13 × 10−3 mol m−2 s−1 Pa−0.5 and 600, respectively. In addition, the H2 flux, N2 flux, and H2/N2 selectivity of the composite membranes remained nearly constant over three heat cycles (under the same conditions), indicating that the structures of the Pd/ceramic/Ti-Al alloy composite membranes were stable.

Combinatorial Studies into the Effect of Thermally Inter-Diffused Magnesium on the Kinetics of Organic Coating Cathodic Delamination from Zinc Galvanized Steel

This paper describes a high-throughput study into the role of Mg in preventing corrosion driven coating disbondment of organic coatings from Zn-Mg alloy galvanized steel. A graded Mg wedge is applied to a hot-dip zinc galvanised steel substrate using physical vapour deposition, and subsequently annealed to produce metallic inter-diffusion and formation of Mg2Zn11 intermetallic. An overcoat of electrically insulating polyvinyl butyral (PVB) is applied and corrosion is initiated from a penetrative coating defect using an aqueous electrolyte. The variation in Mg coating weight across the wedge facilitates a systematic investigation of the effect of Mg on Volta potential and the rate of corrosion driven cathodic coating disbondment using scanning Kelvin probe (SKP) potentiometry. The rate of cathodic disbondment is shown to decrease rapidly even at very low Mg coating weight (corresponding to 25 nm thickness before annealing). The results are explained in terms of the galvanic polarity of the corrosion cell formed between Zn exposed at the defect site, and the intact Zn-Mg layer at the metal-organic coating interface.

Fabrication, characterization, and application of palladium composite membrane on porous stainless steel substrate with NaY zeolite as an intermediate layer for hydrogen purification

Palladium composite membrane with excellent stability was successfully prepared using the electroless plating (ELP) route on a porous stainless steel (PSS) support for hydrogen separation. In order to modify the average pore size of PSS support and to prevent inter-metallic diffusion, the NaY zeolite layer was coated on the PSS support with the seeding and secondary growth method. A high-temperature membrane module was designed by Solid work software and fabricated from 316 L stainless steel with a knife-edge seal. The microstructures and morphologies of the samples were analyzed using XRD, BET, AFM, FESEM and EDX techniques. Permeation experiments were carried out with binary mixtures of H2/N2 with various ratios (90/10, 75/25 and 50/50) and pure H2 and N2 at different temperatures (350, 400 and 450 °C) and feed pressures (200–400 kPa). Hydrogen permeation tests showed that the membrane with a thickness of about 7 μm had a hydrogen permeance of 6.2 × 10−4 mol m−2 s−1 Pa−0.5 with an ideal H2/N2 selectivity of 736, at 450 °C. In addition, the results of stability tests revealed that the membrane could remain stable during a long-term operation by varying temperature and feed gases.

Ultrasonic Spot Welding of an Aluminum Alloy for Automotive Applications

To reduce fuel consumption and the resulting environment-damaging, climate-changing, costly, human death-causing emissions, lightweight aluminum alloys have been increasingly used in the transportation industry due to their low density, high specific strength, superior ductility, machinability, recyclability, and environmental friendliness. The structural applications of such aluminum alloys in the automotive industry unavoidably entail welding and joining process. While it is challenging to weld aluminum sheets via the conventional resistance spot welding developed mainly for joining steel sheets, an emerging solid-state joining technology known as ultrasonic spot welding (USW) is promising for joining aluminum alloys. This study was aimed to examine the feasibility of welding a 6022 Al alloy similarly (AA6022-to-AA6022) and dissimilarly (AA6022-to-ZEK100) in relation to welding energy. It was observed that there was a significant change in the interface grain size in the similar welding, exhibiting a characteristic fine-grained “necklace”-like structure along the welding line, while an intermetallic diffusion layer was present in the dissimilar welding of aluminum-to-magnesium alloys, and its thickness increased as the welding energy increased. The tensile lap shear strength first increased, reached its peak value at a certain energy, and then decreased with increasing welding energy. The strength of the dissimilar welded joints was about 55% of that of the similar welded joints. Three different modes of interfacial failure, nugget pull-out, and transverse through-thickness (TTT) crack growth were observed in the similar welded joints, while only interfacial failure was present in the dissimilar welded joints.

Thermal Analysis and Production of As-Cast Al 7075/6060 Bilayer Billets

Load-adjusted, weight-optimized components can be fabricated by following a multi-material approach. Integrating the respective advantages of strength and corrosion resistance of Al 7075 and Al 6060 into a single structural component leads to a complex property profile. Compound casting offers a high potential in terms of process chain shortening, material efficiency and bonding quality. The present paper focuses on the production of aluminum bilayer billets by multi-step, discontinuous compound casting. Process conditions influencing the formation of a cohesive bond at the interface are investigated. A fundamental thermal analysis is conducted in order to fully characterize the casting alloys. A process window for metallurgical bonding of Al 7075 and Al 6060 can be defined using a combined approach of process parameters and thermophysical data. The primary bonding mechanism is found to be the epitaxial solidification which occurs through remelting and recrystallization of the substrate alloy. Here the dendrite coherence point constitutes a critical level of the near-interface substrate temperature in terms of forming a solid solution. Epitaxy, phase composition and intermetallic diffusion processes are analyzed using SEM–EDS.

Hydrogen-Accelerated Phase Transition and Diffusion in TiO2 Thin Films

TiO2 thin films have received attention as intermetallic diffusion barriers in hydrogen-permeable membranes used for the extraction of purified H2 from chemical reactors. We report the fabrication of thin (∼100 nm) TiO2 films on Si(111) substrates by pulsed laser deposition. Anatase and rutile phases are found to coexist in the as-deposited TiO2 films by X-ray diffraction. Upon H2 annealing at 773–973 K, the phase transformation from anatase to rutile occurs and completes at a strongly (100–380 K) reduced temperature as compared to bulk TiO2. Atomic force microscopy shows that the surface roughness of the thin films increases only slightly (from 3 to 6 nm) in this H-accelerated phase transition. The hydrogen depth distributions in the TiO2 thin films are revealed with resonant 1H(15N,αγ)12C nuclear reaction analysis and evaluated in terms of a one-dimensional diffusion model, which allows the determination of the temperature-dependent diffusion coefficient of hydrogen as D(T) = (5.27 ± 0.89) × 10–8 exp(−0...

Ni-Mn-Ga micro-trusses via sintering of 3D-printed inks containing elemental powders

Ni-Mn-Ga magnetic shape memory alloy (SMA) micro-trusses, suitable for high magnetic field induced strains and/or a large magnetocaloric effect, are created via a new additive manufacturing method combining (i) 3D-printing of ∼400 μm struts with an ink containing a polymer binder and elemental Ni, Mn, and Ga powders, (ii) binder burn-out and metallic powder interdiffusion and homogenization to create the final alloy, and (iii) further sintering to increase strut density. Controlled amounts of hierarchical porosity, desirable to enable twinning in this polycrystalline alloy, are achieved after sintering: (i) continuous, ∼450 μm wide channels between the printed, ∼300 μm diameter Ni-Mn-Ga struts and (ii) microporosity within the struts, from 50 to 200 μm voids where the largest Ga powders initially resided, and from residual 5–25 μm pores between powders due to incomplete sintering. The micro-trusses, sintered at 1000 °C for 12 h, and chemically ordered for 10 h at 700 °C, with overall porosities of 73–76%, have uniform compositions near Ni-32Mn-18Ga (at.%) and are comprised of a non-modulated martensite phase. Reversible martensite/austenite transformations between 45 and 90 °C, Curie temperatures of 85–90 °C, and saturation magnetizations of up to 56 Am2/kg are achieved.

Morphology of Ni (core)/Au (shell) nanoparticles

We obtained sphere-like nanoparticles Ni/Au with a core-shell structure. They are variable in size (7–14 nm of Ni nuclei) and have a narrow-size particle distribution. It was done by means of stepwise (sequential) reduction of the calibrated portions of tetrahydroborate sodium and nickel sulfate solutions. It was done under the presence of sodium citrate as a stabilizer and the combination with a two-step deposition of Au film: (1) electrochemical substitution of Ni0 + Au+3 → Ni+2 + Аu0 and (2) reduction of chloroauric acid by tetrahydroborate sodium. The study of the particles was provided by TEM, XRD, SAXS, CV, ICP OES, and XPS. It significantly allowed to broaden out the existing knowledge on their morphology, phase, and chemical composition. Au shell with averaged 0.6-nm thickness is formed as an irregular polyhedron, composed of polyhedral pieces (scales) with the structure of fcc-type. The shell has pores around the joints of polyhedral pieces. So, Ni nuclei are oxidized under storage of samples at these locations to form nickel hydroxide. The nanophase of solid solution of Au-Ni (rich in gold) is formed on the Ni-Au contact. This is the result of interdiffusion of metals (mainly nickel in gold). Its volume fraction can reach up to 17%. Ni core then contains small amounts of impurities of boron or its compounds.

Diffusion barrier coating using a newly developed blowing coating method for a thermally stable Pd membrane deposited on porous stainless-steel support

In this study, we present an intermetallic diffusion barrier coating using a newly developed blowing coating method for a thermally stable Pd-based composite membrane on porous stainless steel (PSS). A tubular PSS sample with 1/2 inch (12.7 mm) in diameter and 450 mm in length was used for the support. The support was welded with a stainless-steel cap and a 450-mm-long stainless-steel tube for each end. Before the diffusion barrier coating, the large-sized entrance pores were gradually blocked with sub-micron (∼500 nm) and nano (50–80 nm) yttria stabilized zirconia (YSZ). 8YSZ, i.e., 8wt.% YSZ, was used for the interdiffusion barrier material and dispersed on the surface of the pre-treated PSS using the blowing coating method. The blowing coating method has 4 steps: (i) spraying the 17 wt. % 8YSZ paste on the surface of the PSS tube, (ii) blowing the paste using compressed air, (iii) drying at room temperature, and (iv) heat treatment at 923 K for 2 h in air. Steps (i) and (ii) were repeated 3 times to have a ∼240 nm thick 8YSZ layer. A thin palladium layer (∼3 μm) was deposited on the pre-treated PSS using electroless plating, and the membrane stability was tested at 673–773 K for ∼ 200 h. A hydrogen permeation flux of 9.86 × 10−2 mol m−2 s−1 and an H2/N2 selectivity of 595 were obtained at 773 K and a transmembrane pressure difference of 20 kPa. The surface and cross-sectional SEM/EDX analysis confirmed that the 8YSZ layer sufficiently prevented the interdiffusion between Pd and PSS elements, such as Fe, Cr and Ni.

Recent Advances in Pd-Based Membranes for Membrane Reactors.

Palladium-based membranes for hydrogen separation have been studied by several research groups during the last 40 years. Much effort has been dedicated to improving the hydrogen flux of these membranes employing different alloys, supports, deposition/production techniques, etc. High flux and cheap membranes, yet stable at different operating conditions are required for their exploitation at industrial scale. The integration of membranes in multifunctional reactors (membrane reactors) poses additional demands on the membranes as interactions at different levels between the catalyst and the membrane surface can occur. Particularly, when employing the membranes in fluidized bed reactors, the selective layer should be resistant to or protected against erosion. In this review we will also describe a novel kind of membranes, the pore-filled type membranes prepared by Pacheco Tanaka and coworkers that represent a possible solution to integrate thin selective membranes into membrane reactors while protecting the selective layer. This work is focused on recent advances on metallic supports, materials used as an intermetallic diffusion layer when metallic supports are used and the most recent advances on Pd-based composite membranes. Particular attention is paid to improvements on sulfur resistance of Pd based membranes, resistance to hydrogen embrittlement and stability at high temperature.

Simulation of the influence of the interface roughness on the residual stresses induced in (ZrO2+Y2O3)+NiAl-type composite coatings deposited on Inconel 713C

Constant demand for more efficient turbine engines requires applying thermal barrier coatings (TBC) on the crucial engine components. However, one of the main problems encountered in designing new kinds of ceramic coatings intended for high temperature residential components is the residual stresses generated during the exploitation of these components at elevated temperatures. In the present work, thermal barriers (TBC) composed of ZrO2+20%Y2O3 and β-NiAl intermetallic diffusion layers were fabricated on Inconel 713C. The TBCs thus produced were characterized by scanning electron microscopy (SEM). The residual stresses induced in the TBC and TGO (thermally grown oxide) layers during the manufacturing process were analyzed by numerical simulations. The numerical models also permitted analyzing the influence of various interface undulation degrees including the real interface shape (which is reproduced and then introduced into the model). The results obtained showed that the level of residual stress strongly depends on the differences in the properties of the constituent materials and on the undulation ratios of the TBC layers. The numerical simulation of the real shape of the interface between the layers revealed that stress concentration zones occur not only at the peaks and valleys of the interface but also on the semi-flat surface in the midway between them.