Interfacial features of TiAl alloy/316L stainless steel joint brazed with Zr−Cu−Ni−Al amorphous filler metal

TiAl alloy and 316L stainless steel were vacuum-brazed with Zr?50.0Cu?7.1Ni?7.1Al (at.%) amorphous filler metal. The influence of brazing time and temperature on the interfacial microstructure and shear strength of the resultant joints was investigated. The brazed seam consisted of three layers, including two diffusion layers and one residual filler metal layer. The typical microstructure of brazed TiAl alloy/316L stainless steel joint was TiAl alloy substrate/α₂-(Ti₃Al)/AlCuTi/residual filler metal/Cu₉Zr₁₁+Fe₂₃Zr₆/Laves-Fe₂Zr/α-(Fe,Cr)/316L stainless steel substrate. Discontinuous brittle Fe₂Zr layer formed near the interface between the residual filler metal layer and α-(Fe,Cr) layer. The maximum shear strength of brazed joints reached 129 MPa when brazed at 1020 °C for 10 min. The diffusion activation energies of α₂-(Ti₃Al) and α-(Fe,Cr) phases were ?195.769 and ?112.420 kJ/mol, respectively, the diffusion constants for these two phases were 3.639×10^?6 and 7.502×10^?10 μm²/s, respectively. Cracks initiated at Fe₂Zr layer and propagated into the residual filler metal layer during the shear test. The Laves-Fe₂Zr phase existing on the fracture surface suggested the brittle fracture mode of the brazed joints.     

First Stages of Oxidation of Pt-Modified Nickel Aluminide Bond Coat Systems at Low Oxygen Partial Pressure

The θ-Al₂O₃?→?α-Al₂O₃ phase transformation was investigated in thermally grown oxide formed on β-(Ni,Pt)Al bond coats during isothermal exposures at 900–1,200?°C in an argon atmosphere stream with the O₂ partial pressure of 1?×?10^?5?atm. Local curve fitting was used to evaluate the evolution of the parabolic rate constant, k _p , using a general kinetic model (t?=?A?+?BΔm?+?CΔm ²), during the first 5?h of oxidation. All net mass–gain curves exhibited deviations from the classic parabolic model, Δm?=?k _p t ^?; a steady state regime was established only after 4?h of exposures, except for the sample oxidized at 1,100?°C.     

Influence of Zinc on Coarsening of δ-Ni<Subscript>2</Subscript>Si Particles,Aging Behavior and Hardness in a Cu-Ni-Si Alloy

In the present paper, the aging precipitation and coarsening of disk-like δ-Ni₂Si particles in Cu and Cu-10Zn alloys aged at 450 °C have been investigated by hardness, electric resistivity measurement and transmission electron microscopy observation. The coarsening dynamics of the average diameter of the δ-Ni₂Si particles coincides with the t ^1/3 time law for both alloys. The coarsening of the diminution of supersaturation related to aging time t coincides with the t ^?1/3 time rule. Adding Zn to the Cu-Ni-Si alloy increases the growth and coarsening rate of the particles mainly because of the increased diffusivity D of the δ-Ni₂Si particles in the matrix. The value of D of the δ-Ni₂Si particles in the Cu-xZn (x = 0, 10 wt.%) matrix and the Cu/δ-Ni₂Si interfacial energy γ are independently calculated by using the Lifshitz–Slyozov–Wagner theory which was extended to include disk-like particles by Boyd and Nicholson. The values of D and γ increase from 0.77 × 10^?19 to 2.21 × 10^?19 m²/s and 0.19 to 0.63 J/m², respectively, when Zn is added to the Cu-Ni-Si alloy. These calculations and the analysis show that the properties of Cu-Ni-Si-Zn alloy can significantly be enhanced by reducing the aging temperature.     

Hot deformation behavior of TiAl alloys prepared by blended elemental powders

A nearly full dense Ti-45Al-7Nb-0.4W (at.%) alloy billet with dimension of 120 mm in diameter and 50 mm in height was fabricated by reactive sintering of blended elemental powders. The high temperature deformation behavior was investigated by isothermal compressive tests, performed at temperature in 1000–1200 °C with strain rates from 1 × 10^?3 s^?1 to 1 × 10^?1 s^?1. Results indicate that the dependence of flow stress on temperature and strain rate is well fit for a hyperbolic-sine relationship using the Zener–Hollomon parameter. The measured apparent activation energy Q and stress exponent are determined as 420 kJ mol^?1 and 3.7, respectively. High oxygen content, high Nb content and fine grain size are main reasons for the high activation energy and high strength of PM TiAl alloy. An appropriate set of deformation processing parameters of 1200 °C and 1 × 10^?3 s^?1 are recommended for the present TiAl alloy.     

Growth behavior and microstructure of intermetallics at interface of AuSn20 solder and metalized-Ni layer

The AuSn20/Ni joints were prepared by the reflow soldering technology and then annealed at solid-state temperature to form diffusion couples. The interfacial reactions and the growth kinetics of the intermetallic compounds (IMC) at the AuSn20/Ni soldering interface were investigated by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The results show that, the (Ni,Au)₃Sn₂ phases are formed at the AuSn20/Ni interface after soldering at 583 K. The thickness l of the IMC layer monotonically increases with increasing annealing time t according to the relationship l=k(t/t₀)ⁿ, where the exponent n is 0.527, 0.476 and 0.471 for 393, 433 and 473 K annealing, respectively. This indicates that the volume diffusion contributes to the growth of the IMC layer at the AuSn20/Ni interface at solid-sate temperature. The pre-exponential factor K₀=1.23×10^?7 m²/s and the activation enthalpy Q_K=81.8 kJ/mol are obtained from the results of the parabolic coefficient K by a least-squares method.     

A study of the film formation kinetics on zinc in different acidic corrosion inhibitor solutions by quartz crystal microbalance

Chromates conversion coatings provide very effective corrosion protection for many metals. However, the high toxicity of chromate leads to an increasing interest in using non-toxic alternatives such as molybdates, silicates, rare earth metal ions and etc. In this work, quartz crystal microbalance (QCM) was applied as an in-situ technique to follow the film formation process on zinc (plated on gold) in acidic solutions containing an inorganic inhibitor, i.e. potassium chromate, sodium silicate, sodium molybdate or cerium nitrate. Using an equation derived in this work, the interfacial mass change during the film formation process under different conditions was calculated, indicating three different film formation mechanisms. In the presence of K₂CrO₄ or Na₂SiO₃, the film growth follows a mix-parabolic law, showing a process controlled by both ion diffusion and surface reaction. The apparent kinetic equations are 0.4t = −17.4 + 20Δm_f + (Δm_f)² and 0.1t = 19.0 + 8.4Δm_f + 10(Δm_f)² respectively (t and Δm are in seconds and μg/cm²). In solutions containing Na₂MoO₄, a logarithmic law of Δm_f = −24.7 + 6.6 ln t was observed. Changing the inhibitor to Ce(NO₃)₃, the film growth was found to obey an asymptote law that could be fit into the equation of Δm_f = 55.1(1 − exp(−2.6 × 10⁻³t)).     

Microstructure and properties of high silicon aluminum alloy with 2% Fe prepared by rheo-casting

The morphology changes of both Fe-containing intermetallic compounds and the primary Si phase of Al-20Si-2Fe- 2Cu-0.4Mg-1.0Ni-0.5Mn (mass fraction, %) alloy produced by semi-solid rheo-diecasting were studied. The semi-solid slurry of high silicon aluminum alloy was prepared by direct ultrasonic vibration (DUV) which was imposed on the alloy near the liquidus temperature for about 2 min. Then, standard test samples of 6.4 mm in diameter were formed by semi-solid rheo-diecasting. The results show that the DUV treatment suppresses the formation of needle-like β-Al₅(Fe, Mn)Si phase, and the Fe-containing intermetallic compounds exist in the form of fine Al₄(Fe, Mn)Si₂ particles. Additionally, the primary Si grows up as fine and round particles with uniform distribution in a(Al) matrix of this alloy under DUV treatment. The tensile strengths of the samples at the room temperature and 573 K are 230 MPa and 145 MPa, respectively. The coefficient of thermal expansion (CTE) between 25 °C and 300 °C is 16.052 8×10^?6 °C^?1, and the wear rate is 1.55%. The hardness of this alloy with 2% Fe reaches HB146.3. It is discovered that modified morphology and uniform distribution of the Fe-containing intermetallic compounds and the primary Si phase are the main reasons for reducing the CTE and increasing the wear resistance of this alloy.     

Removal of Co(Ⅱ) from aqueous solutions by NKC-9 strong acid resin

A strong acidic ion exchange resin(NKC-9)was used as a new adsorbent material for the removal of Co(Ⅱ)from aqueous solutions.The adsorption isotherm follows the Langmuir model.The maximum adsorption capacity of the resin for Co(Ⅱ)is evaluated to be 361.0 mg/g by the Langmuir model.It is found that 0.5 mol/L HCl solution provides effectiveness of the desorption of Co(Ⅱ)from the resin.The adsorption rate constants determined at 288,298 and 308 K are 7.12×10-5,8.51×10-5and 9.85×10-5s-1, respectively.The apparent activation energy(Ea)is 12.0 kJ/mol and the adsorption parameters of thermodynamic are-H Θ=16.1 kJ/mol,-SΘ=163.4 J/(mol·K),-G Θ 298 K=-32.6 kJ/mol,respectively.The adsorption of Co(Ⅱ)on the resin is found to be endothermic in nature.Column experiments show that it is possible to remove Co(Ⅱ)ions from aqueous medium dynamically by NKC-9 resin.     

Surface characteristics, corrosion behavior, and antibacterial property of Ag-implanted NiTi alloy

NiTi shape memory alloy was modified by Ag ion implantation with different incident doses to improve its antibacterial property. The atomic force microscopy, auger electron spectroscopy, and X-ray photoelectron spectroscopy show that the surface of NiTi alloy is covered by TiO₂ nano-film with embedded pure Ag with a peak concentration of 5.0 at% at the incident dose of 1.5 × 10¹⁷ ions·cm^?2, and Ni concentration is reduced in the superficial surface layer. The surface roughness reaches the maximum value nearly twice higher than the control sample at the incident dose of 1.5 × 10¹⁷ ions·cm^?2. The potentiodynamic anodic polarization curves show that the Ag-implanted NiTi samples possess higher self-corrosion potential (E _corr) and lower self-corrosion current density (i _corr) but lower breakdown potential (E _br). Therefore, the corrosion resistance of the Ag–NiTi is comparable to, if not better than, the untreated NiTi. The antibacterial tests reveal that there is a distinct reduction of the germ numbers on the Ag–NiTi, which is due to the direct contact between Ag and germ, and enhanced by the leaching Ag ions.     

搅拌摩擦焊AA7075-T651铝合金接头的疲劳裂纹扩展(英文)

研究12 mm厚AA7075-T651铝合金板搅拌摩擦焊接头的疲劳裂纹扩展行为。从搅拌摩擦焊接头以及母材中截取试样,对试样进行疲劳裂纹扩展实验。对搅拌摩擦焊接头以及母材的横向拉伸性能进行评估。用光学显微镜和透射电镜分析焊接接头的显微组织。用扫描电镜观察试样的断裂表面。与母材相比,焊接接头的ΔKcr降低了10×10-3 MPa·m1/2。搅拌摩擦焊AA7075-T651接头的疲劳寿命明显低于母材的,其原因可归结于焊缝区的析出相在搅拌摩擦焊接过程中的溶解。     

Characteristic features of diffusion induced grain boundary migration for Σ9 [110] asymmetric tilt boundaries in the Cu(Zn) system

The characteristic features of diffusion induced grain boundary migration (DIGM) in the Cu(Zn) system were experimentally studied for [110] asymmetric tilt boundaries using Cu bicrystals annealed at 693 K for various times by a capsule zincification technique. The experiment was carried out for the boundaries with inclination angles of φ=0, 20, 35, 55, 65 and 90° and with a constant misorientation angle of θ=39° (Σ9). During annealing, the grain boundary migrates towards a crystal grain of larger coherency strain energy with higher probability due to DIGM. Taking elastic anisotropy of each crystal grain into consideration, the difference between the probabilities of grain boundary migration towards both side grains can be accounted for by the coherency strain model proposed by Hillert. The migration rate v of the moving boundary is almost constant regardless of the annealing time t between t=72 and 384 h (2.59×10⁵ and 1.38×10⁶ s). The value of v monotonically decreases with increasing inclination angle. This implies that the boundary diffusion coefficient of Zn in Cu is a monotone decreasing function of the inclination angle. The experimental results on the kinetics at the steady state stage were theoretically analyzed using the energy balance model proposed by Kajihara and Gust (Scripta mater., 1998, 38, 1621. The analysis indicates that the effective driving force Δ^efG for the grain boundary migration is merely one-thirtieth of the chemical driving force, whereas it still remains three times greater than the minimum value corresponding to the coherency strain energy during DIGM under the present experimental conditions. The mobility of the moving boundary was evaluated to be M=3.77×10⁻¹⁷ m⁴/Js from the values of v and Δ^efG according to the relationship M=v/Δ^efG. This value of M is close to the results estimated by Yamamoto et al. (Acta mater., 1999, 47, 1757) for the [100] twist and random boundaries in the Cu(Zn) system.     

Interstitial and substitutional diffusion of metallic solutes in Ti3Al

Solute diffusion of Ni, Fe and Nb in the intermetallic compound Ti₃Al was studied. The diffusion measurements of Ni and Fe were performed with radiotracers applying the standard precision grinding technique for sectioning, while the concentration profiles of Nb in Ti₃Al were analysed through in-depth profiling by secondary ion mass spectrometry (SIMS). Ni and Fe exhibit fast diffusion behaviour of about 4 and 2 orders of magnitude, respectively, larger than titanium self-diffusion. The temperature dependencies of the diffusion coefficients yield the Arrhenius parameters D₀^Ni=1.76 × 10⁻⁵ m²/s, Q^Ni=195 kJ/mol and D₀^Fe=1.96 × 10⁻³ m²/s, Q^Fe=277.2 kJ/mol, respectively. The high mobility of these solutes with comparatively small atomic radii suggests in the D0₁₉-structure of Ti₃Al some type of interstitial diffusion that is discussed in the context of results of analogous diffusion investigations in α-Ti. Nb-diffusion coefficients in Ti₃Al were found to be lower by about one order of magnitude than self-diffusion. The Arrhenius relation is characterized by D₀^Nb=3.15 × 10⁻⁴ m²/s and Q^Nb=338.7 kJ/mol. It is concluded that Nb-diffusion occurs substitutionally via thermal vacancies in the Ti-sublattice.     

Analysis of alloying systems of clad stamping tools for cold deformation of metal (review)

Two alloying systems of stamping tools (with intermetallic and carbide hardening) are analysed. Analysis shows the high characteristics of the metal with different alloying systems. The heat resistance of the 100Kh4M5F2(Zr) alloy is not inferior to the R18 high-speed tool steel, and the hardness equals 58–62 HRC as a result of carbide hardening. The relative wear resistance of the 8Kh4GSV2M5F2T alloy was (ε = 2.65), impact toughness (0.28 MJ/m²) and hardness (55 HRC). The highest wear resistance was recorded for the K15M15N5Kh3B2 alloy with the following properties after heat treatment: impact toughness (0.1 MJ/m²) and hardness (39 HRC). The wear resistance is 2–2.5 times higher than that of the R18 high-speed tool steel and 6–6.5 times higher than that of Cr12 and Cr12Mo steels.     

Preparation and spectroscopic, and thermal decomposition kinetic studies of europium（Ⅲ） complex [Eu（HNBD）3] （HNBD： 1-（6-hydroxy-1-naphthyl）-1,3-butanedione）

The complex of Eu（IH） with 1-（6-hydroxy- 1-naphthyl）- 1,3-butanedione （HNBD） was prepared for the first time and characterized by elemental analysis, IR, UV, fluorescence spectrum, and DTA-TG-DTG techniques. The IR and UV-visible spectra showed that Eu（Ⅲ） ion was coordinated to the HNBD ligand. The fluorescence spectrum showed the presence of Eu^3＋ characteristic emission. The TG-DTA-DTG curves showed that the thermal decomposition of the anhydrous complex was a two-stage process and the final residue was Eu2O3. The thermal decomposition kinetic parameters of the complex were evaluated from TG-DTG data by using three kinds of integral methods （Coat-Redfem equation, Horowitz and Metzger equation, Madhusudanan-Krishnan-Ninan equation）. The kinetic parameters of the first stage are E^＊ = 164.02 kJ.moll, A = 1.31 × 10^15 s^-l, AS^＊= 42.27 J·K^-l·mol^-l, △H^＊ = 159.51 kJ·mol^-l, △G^＊= 136.54 kJ·mol^-l, and n = 3.1, those of the second stage are E^＊= 128.52 kJ·mol^-l, A = 1.44× 106 s^-1, △S^＊= - 136.89 J·K^-l·mol^-l, △H^＊ = 120.41 kJ·mol^-l, △G^＊= 283.85 kJ·mol^-l, and n = 1.1.     

Gas sensing properties of SnO2 nanoparticles mixed with gold nanoparticles

SnO₂ nanoparticles mixed with different amounts of gold nanoparticles (GNPs) were synthesized and their CO sensing properties were investigated. The sol–gel method was employed to prepare the initial solution. SEM, TEM, XRD, DLS and spectrophotometry were used to characterize the nanoparticles. The pure sensors showed a response of about 4 to 12.8 for (20–80)×10^?6 CO at operating temperature of 340 °C. The response and recovery time at 50×10^?6 Co is about 10 and 14 s, respectively. The amount of GNPs optimized was used to create high performance GNP-SnO₂ sensors (m(Au)/m(Sn)=3.7663×10^?4) and optimal operating temperature was about 260 °C and the response at concentrations of (20–80)×10^?6 was 8.3 to 29.5, respectively.     

A Study on the Passivation Behavior and Semiconducting Properties of Gamma Titanium Aluminide in 0.1 N H2SO4, HNO3, and HClO4 Acidic Solutions

The study focuses on the passivation behavior of single-gamma-phase titanium aluminide in acidic solutions with a particular emphasis on the role of oxidizing strength in characteristics of passive layer. The report includes potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies along with Mott-Schottky analysis in order to determine the corrosion behavior of the alloy and the semiconducting properties of the scale formed during exposure to acidic environment. Passive current density measured from potentiodynamic polarization curve, polarization resistance (R _p) estimated by EIS, defect density, and flatband potential drawn from Mott-Schottky analysis are mainly used in estimating the ability of passive film formed on alloy in protecting it against high corrosion rates in Sulfuric acid (a non-oxidizing acid), perchloric acid, and nitric acid (oxidizing acid with different oxidizing strength). The results show that passive current density (i _pass) in Sulfuric acid is 2.67 × 10^?5 A cm^?2, which is 2.5 and 3 times greater than the values obtained in perchloric acid (i _pass = 9.91 × 10^?6) and nitric acid (i _pass = 7.98 × 10^?6), respectively. EIS data reveal that the value of R _p in sulfuric acid (20 kΩ cm²) is about three and five times smaller than that its value in perchloric acid and Nitric acid, respectively. Mott-Schottky analysis shows that the passive layer exhibits an n-type semiconducting characteristics irrespective of acidic environment. The greatest and the smallest values of donor density (N _D) are obtained for the passive scale formed in sulfuric acid (N _{D, H2SO4} = 18.36 × 10¹⁹) and nitric acid (N _{D, HNO3} = 13.13 × 10¹⁹), respectively. The report concludes that characteristics of the passive scale are directly affected by reduction potential of the acid, which is the criterion of its oxidizing strength. An increase in the oxidizing strength of the acidic solution results in formation of more protective and less conductive layer on γ phase titanium aluminide.     

Interfacial reaction in (Mg-37.5Al)/(Mg-6.7Nd) diffusion couples

The solid-state diffusion reaction between Mg-37.5Al and Mg-6.7Nd was studied in the 623-673 K temperature range. A solid-liquid contact method was employed to produce diffusion couples. The Al₄Nd, Al₁₁Nd₃, Al₃Nd and Al₂Nd intermetallic compounds form in the diffusion reaction layers of the couples. The formation of intermetallic compounds in the diffusion reaction layers is rationalized using the Miedema model. The local average compositions through the diffusion reaction layer were determined, and used to construct a semi-quantitative diffusion path on the isothermal Mg-Al-Nd ternary phase diagram at 673 K. The growth constants of the entire diffusion reaction layers were determined as 8.91 (±0.94)×10^-14 m²/s, 1.39 (±0.15)×10^-13 m²/s and 1.93 (±0.38)×10^-13 m²/s at 623 K, 648 K and 673 K, respectively. The activation energy Q for the growth of the entire diffusion reaction layers was 54±4.6 kJ/mol.     

Superplastic behavior of a powder metallurgy TiAl alloy with a metastable microstructure

Superplasticity in a powder metallurgy (P/M) TiAl alloy (Ti–47Al–2Cr–1Nb–1Ta) with a metastable B2 phase coexisted with a fine-grained γ+α₂ duplex structure has been studied. Alloy samples were tested at temperatures ranging from 650 to 1100°C, and at strain rates ranging from 10⁻⁶ to 10⁻⁴ s⁻¹. An elongation of over 300% was obtained at a strain rate of 2×10⁻⁵ s⁻¹ and at a temperature of 800°C, which is close to the ductile-to-brittle transition temperature of the alloy. This is in contrast to the prior observations of superplastic behavior of TiAl alloys in which a typical temperature of 1000°C is usually required for achieving superplasticity. It is suggested that the occurrence of low-temperature (800°C) superplasticity in the present alloy is primarily due to the presence of a metastable B2 phase in addition to a fine-grained (α₂+γ) duplex microstructure. The metastable B2 phase continues to decompose into fine-grained α₂ and γ phases, which promotes grain boundary sliding during superplastic deformation. The retained fine B2 grains accommodate the sliding strains to reduce the propensity of cavitation at grain triple junctions and thus delay the cavitation and fracture process.     

Microwave Power Absorption in Materials for Ferrous Metallurgy

The characteristics of microwave power absorption in materials for ferrous metallurgy, including iron oxides (Fe₂O₃, Fe₃O₄ and Fe₀.₉₂₅O) and bitumite, were explored by evaluating their dielectric loss (Q _E) and/or magnetic loss (Q _H) distributions in the 0.05-m-thick slabs of the corresponding materials exposed to 1.2-kW and 2.45-GHz microwave radiation at temperatures below 1100°C. It is revealed that the dielectric loss contributes primarily to the power absorption in Fe₂O₃, Fe_0.925O and the bitumite at all of the examined temperatures. Their Q _E values at room temperature and slab surface are 9.1311 × 10³ W m^?3, 23.7025 × 10³ W m^?3, and 49.5999 × 10³ W m^?3, respectively, showing that the materials have the following heating rate initially under microwave irradiation: bitumite > Fe_0.925O > Fe₂O₃. Compared with the other materials, Fe₃O₄ has much stronger power absorption, primarily originated from its magnetic loss (e.g., Q _H = 1.0615 × 10⁶ W m^?3, Q _H/Q _E = 2.4185 at 24°C and slab surface), below its Curie point, above which the magnetic susceptibility approaches to zero, thereby causing a very small Q _H value at even the surface (Q _H = 1.0416 × 10⁵ W m^?3 at 880°C). It is also demonstrated that inhomogeneous power distributions occur in all the slabs and become more pronounced with increasing temperature mainly due to rapid increase in permittivity. Characterizing power absorption in the oxides and the coal is expected to offer a strategic guide for improving use of microwave energy in ferrous metallurgy.     

Isothermal Oxidation Comparison of Three Ni-Based Superalloys

Ni-based superalloys are used for high-temperature components of gas turbines in both industrial and aerospace applications due to their ability to maintain dimensional stability under conditions of high stress and strain. The oxidation resistance of these alloys often dictates their service lifetime. This study focuses on the isothermal oxidation behavior of three Ni-based superalloys, namely, polycrystalline cast IN738LC, single-crystal N5, and a ternary Ni-Fe-Cr (TAS) powder metallurgy alloy. The isothermal oxidation tests were conducted at 900 °C in the static air up to 1000 h, and the specific aspects studied were the oxidation behavior of these chromia-forming and alumina-forming alloys that are used extensively in industry. In particular, the behavior of oxide scale growth and subsurface changes were analyzed in detail using various techniques such as SEM, EDS, and AFM. From the isothermal oxidation kinetics, the oxidation rate constant, k _p, was calculated for each alloy and found to be; k _p = 2.79 × 10^?6 mg² cm^?4 s^?1 for IN738LC, k _p = 1.42 × 10^?7 mg² cm^?4 s^?1 for N5 and k _p = 1.62 × 10^?7 mg² cm^?4 s^?1 for TAS. Based on a microstructural analysis, IN738LC exhibited a continuous dense outer scale of Cr₂O₃ and discontinuous inner scale of Al₂O₃, whereas N5 and TAS showed a dense outer scale of Al₂O₃ alone. The results suggested that the N5 and PM-TAS alloys are more oxidation resistant than the IN738LC under these conditions.