Assessment of a powder metallurgical processing route for refractory metal silicide alloys

A powder metallurgical (PM) processing route for the manufacturing of two different refractory metal silicide alloys comprising inert gas atomization of presintered bars, hot isostatic pressing, and hot extrusion (reduction in cross section of 6:1) was established. The mechanical properties between room temperature and 1200 °C of the PM-processed Mo-3Si-1B and Nb-24Ti-20Si-5Cr-3Hf-2Al alloys (in wt pct) were assessed with tensile tests vs a state-of-the-art Ni-base single crystalline alloy (CMSX 4) and a directionally solidified (MASC) niobium-base silicide alloy, respectively. The microstructural characterization of both the hot-isostatically pressed and extruded materials was carried out applying scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray diffraction (XRD) analysis. The Mo-Si-B alloy is characterized by an intermetallic matrix surrounding globular Mo particles in the hot isostatic press and a nearly continuous molybdenum solid solution matrix with dispersed intermetallic particles in the hot-extruded condition. Hot extrusion results in a substantial reduction of the DBTT of about 200 °C and tensile strengths superior to CMSX 4 at temperatures above 1000 °C. In the case of the Nb-base silicide alloy, a niobium solid solution surrounding intermetallic particles with Nb₅Si₃-type structure characterizes the final alloy. In the intermediate temperature range of 500 °C to 816 °C, a strength level equivalent to the directionally solidified MASC alloy was observed. This article is based on a presentation made in the symposium entitled “Beyond Nickel-Base Superalloys,” which took place March 14–18, 2004, at the TMS Spring meeting in Charlotte, NC, under the auspices of the SMD-Corrosion and Environmental Effects Committee, the SMD-High Temperature Alloys Committee, the SMD-Mechanical Behavior of Materials Committee, and the SMD-Refractory Metals Committee.     

Composite materials with an intermetallic matrix based on nickel and titanium monoaluminides hardened by oxide particles or fibers

Hardening phase/intermetallic matrix pairs are chosen for composite materials (CMs) intended for long-term high-temperature operation. These materials must have high and stable mechanical properties during a long time at high temperatures and loads. The compatibility of the physicochemical and mechanical properties of CM components is estimated to choose hardening phase/intermetallic matrix pairs in which the matrix is represented by an alloy based on NiAl or TiAl monoaluminide and the hardening phase is a refractory thermodynamically stable oxide of a Group III transition metal M ₂O₃. The following two schemes are used to perform hardening of a CM with a matrix consisting of a TiAl or NiAl alloy by the most thermodynamically stable interstitial phases, i.e., refractory oxides, at temperatures higher than the operating temperature (T _op) of the IMM. The first scheme consists in creating Al₂O₃/TiAl CMs hardened by continuous single-crystal sapphire fibers using the impregnation of a bundle of single-crystal fibers with a matrix melt followed by directional solidification. The TiAl-based matrix in these CMs serves as a binder connecting oxide phase fibers and preventing them from fracture due to high adhesion forces between oxide fibers and the matrix and a high fiber/matrix interface strength. In the second scheme, Y₂O₃/NiAl CMs are produced by powder metallurgy methods, which include severe deformation by extrusion accompanied by the formation of deformation texture and subsequent recrystallization annealing. In these CMs, disperse refractory oxide particles stabilize grain boundaries in a recrystallized matrix material and lead to the formation of directional structures with coarse elongated grains and a low fraction of transverse boundaries. Al₂O₃/TiAl CMs containing 20–25 vol % hardening single-crystal sapphire Al₂O₃ fibers can operate at temperatures of 1000–1050°C (∼0.7T _m of matrix), which is 250–300°C higher than the maximum values of T _op of a TiAl-based matrix and 400-450°C higher than the maximum values of T _op of a Ti-based matrix. An Y₂O₃/NiAl composite with a directionally recrystallized structure of a NiAl-based matrix hardened by 2.5 vol % Y{ia2}O₃ particles can be recommended for operation at temperatures of 1400–1500°C ((0.8–0.9)T _m of matrix), which are higher by 100–400°C than not only T _op but also T _m of Ni superalloys.     

Effect of alloying elements on the structure and properties of Al-Li-Cu cast alloys

The structure and mechanical and service properties of Al-Li-Cu alloys are determined, and the results obtained are used to find the effect of major and additional components on their properties and to design a high-strength heat-treatable cast alloy with a low density. After quenching and maximum-strength aging, this alloy has the following level of mechanical properties (casing in a metal mold): σ_u = 360–370 MPa and δ = 6.0–7.5%.     

Selection of Initial Mold–Metal Interface Heat Transfer Coefficient Values in Casting Simulations—a Sensitivity Analysis

Mold–metal interface heat transfer coefficient values need to be determined precisely to accurately predict thermal histories at different locations in automotive castings. Thermomechanical simulations were carried out for Al-Si alloy casting processes using a commercial code. The cooling curve results were validated with experimental data from the literature for a cylindrical-shaped casting. Our analysis indicates that the interface heat transfer coefficient (IHTC) initial value choice between chill–metal and the sand mold–metal interfaces has a marked effect on the cooling curves. In addition, after choosing an IHTC initial value, the solidification rates of the alloy near the chill–metal interfaces varied during subsequent cooling when the gap began to form. However, the gap formation, which results in an IHTC change from the initial value, does not affect the cooling curves within the vicinity of the sand–metal interface. Optimized initial IHTC values of 3000 and 7000 W m⁻²-K⁻¹ were determined for a sand–metal interface and a chill (steel or copper)–metal interfaces, respectively. The initial IHTC had a significant effect on the prediction of secondary dendrite arm spacing (SDAS) (varying between approximately 15 microns and 70 microns) and ultimate tensile strength (UTS) (varying between approximately 250 MPa and 370 MPa) for initial IHTC values that were less than the optimized value of 7000 W m⁻² K⁻¹ for the chill–metal interfaces.     

Influence that nanosecond electromagnetic pulses have on the acquisition of tin and the properties of its alloys

It is established experimentally that the influence that nanosecond electromagnetic pulses (NEMPs) have on the charge melt during the carbothermic reduction of cassiterite in the Na₂CO₃-NaNO₃ medium (1: 0.3) at t = 900–950°C accelerates the formation of the metal phase by a factor of ∼2 and affects its composition. As the duration of irradiation increases to 30 min, the tin content in the crude alloy increases to ∼95%. The influence that the NEMP treatment of the bronze melt has on its physicomechanical properties is revealed. It is shown that the influence of pulses for 10–15-min increases the alloy density to 8.92 g/cm³, hardness by a factor of 1.24, and thermal conductivity by a factor of 2.     

Aluminum matrix composites: Fabrication and properties

Aluminum alloy matrix composites containing 1 to 30 wt pct of fibrous and particulate nonmetals varying in size from 0.06 μm to 840 μm were fabricated. The composites were cast into cylindrical molds for friction and wear tests, hot extrusion and tensile tests. The distribution of the nonmetals in the cast ingots was homogeneous. Friction and wear tests were done on a pin (52100 bearing steel) and dish type machine without lubrication. It was found that composites containing ∼10 wt pct or more of SiC, TiC, Si₃N₄, Al₂O₃, glass, solid waste slag, and silica sand wear less than the pure matrix alloy, but have slightly higher average coefficients of friction. Wear in composites containing soft particles, especially MgO and boron nitride was higher than the pure matrix alloy. The average coefficient of friction of all the composites was in the range of 0.35 to 0.58. Increasing the sliding velocity reduced this range to ∼ 0.4 to 0.45. The longitudinal tensile properties of the extruded composites (with the exception of loss of ductility in some cases) are comparable to that of the matrix alloys. Improvements in strength or ductility were noted. For example, addition of 15 wt pct of 3 μm size Al₂O₃ particles raised the yield and ultimate strength of the Al-4 pct Cu-0.75 pct Mg alloy matrix from 227 to 302 MPa, and 356 to 403 MPa, respectively. The corresponding percent elongation decreased from 25.8 to 12.5. The fact that the various composites can be readily cast and hot formed suggests a variety of engineering applications. AKIRA SATO, formerly Visiting Scientist at Massachusetts Institute of Technology, Cambridge.     

Some observations of diffusional flow in a superplastic alloy

A metallographic study has been made of the denuded zones from diffusional flow in a hydrided alloy of magnesium with 6 wt pct Zn and 0.5 wt pct Zr (ZK 60). At the deformation temperature of 450°C, with an initial grain size of 18 um, the alloy was superplastic. Its maximum strain-rate sensitivity,m = (d log σ)/(d log ∈), was ⊥0.6 at fe –⁴ 10~⁴ sec–¹. A diffusional strain, ed = ΔL_d/L_d, was calculated from measurements of zone thickness, ΔL_d, and interzone distance,L _d. This was a reasonably constant fraction of the total strain,e, up to the limiting strain of ⊥220 pct. Over a strain-rate range of 3.3 x 10–³ sec–¹ to 3.3 x 10⊥⁵ sec–¹,e _d /e increased from about 0.05 to 0.30.     

Creep strengthening in a discontinuous SiC-Al composite

High-temperature strengthening mechanisms in discontinuous metal matrix composites were examined by performing a close comparison between the creep behavior of 30 vol pct SiC-6061 Al and that of its matrix alloy, 6061 Al. Both materials were prepared by powder metallurgy techniques. The experimental data show that the creep behavior of the composite is similar to that of the alloy in regard to the high apparent stress exponent and its variation with the applied stress and the strong temperature dependence of creep rate. By contrast, the data reveal that there are two main differences in creep behavior between the composite and the alloy: the creep rates of the composite are more than one order of magnitude slower than those of the alloy, and the activation energy for creep in the composite is higher than that in the alloy. Analysis of the experimental data indicates that these similarities and differences in creep behavior can be explained in terms of two independent strengthening processes that are related to (a) the existence of a temperature-dependent threshold stress for creep, τ₀, in both materials and (b) the occurrence of temperature dependent load transfer from the creeping matrix (6061 Al) to the reinforcement (SiC). This finding is illustrated by two results. First, the high apparent activation energies for creep in the composite are corrected to a value near the true activation energy for creep in the unreinforced alloy (160 kJ/mole) by considering the temperature dependence of the shear modulus, the threshold stress, and the load transfer. Second, the normalized creep data of the composite fall very close to those of the alloy when the contribution of load transfer to composite strengthening is incorporated in a creep power law in which the applied stress is replaced by the effective stress, the stress exponent,n, equals 5, and the true activation energy for creep in the composite,Q _c , is equal to that in the alloy. formerly Research Associate, Materials Section, Department of Mechanical and Aerospace Engineering, University of California This article is based on a presentation made in the symposium entitled “Creep and Fatigue in Metal Matrix Composites” at the 1994 TMS/ASM Spring meeting, held February 28–March 3, 1994, in San Francisco, California, under the auspices of the Joint TMS-SMD/ASM-MSD Composite Materials Committee.     

Technical study for fabrication of new cermet used as inert anode in aluminum molten-salt electrolysis

In aluminum electrolysis industry, traditional carbon electrodes have many disadvantages under molten-salt corrosive conditions (970°C), such as large quantities of CO₂ production and quick consumption of carbon. The best way is cermet, which is a kind of graded composite material and consists of spinel NiFe₂O₄ as a ceramic phase and Ni-Fe-X alloy as a metal phase. The fabrication of NiFe₂O₄ powder is studied by chemical co-precipitation method with different co-precipitation chemicals (NH₃· H₂O, NaOH); differential thermal analysis and thermal gravity (TG) test have also been carried out to evaluate the performance of fabricated powder. The fabrication of Ni-Fe-X alloy is studied with three different kinds of powder compositions (NiFeAlCuZn, NiFeAlCuSn, and NiFe), different forming methods and sinter conditions are also compared and discussed in detail. DTA, XRD, density, hardness and anti-oxidation tests are carried out to test the performance of fabricated materials. Finally, fabrication technical condition of cermet is studied and determined according to graded composite slurry casting method, which combines the ceramic phase and metal phase with good performance. The fabrication technique presented in this study is valuable for making new anti-corrosion electrode material used in aluminum electrolysis. Published in Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 52–61, 2007.     

Preparation and casting of metal-particulate non-metal composites

A new process for the preparation and casting of metal-particulate non-metal composites is described. Particulate composites of ceramic oxides and carbides and an Al-5 pet Si-2 pct Fe matrix were successfully prepared. From 10 to 30 wt pct of A1₂O₃, SiC, and up to 21 wt pct glass particles, ranging in size from 14 to 340 ώ were uniformly distributed in the liquid matrix of a 0.4 to 0.45 fraction solid slurry of the alloy. Initially, the non-wetted ceramic particles are mechanically entrapped, dispersed and prevented from settling, floating, or agglomerating by the fact that the alloy is already partially solid. With increasing mixing times, after addition, interaction between the ceramic particles and the liquid matrix promotes bonding. Efforts to mix the non-wetted particles into the liquid alloy above its liquidus temperature were unsuccessful. The composite can then be cast either when the metal alloy is partially solid or after reheating to above the liquidus temperature of the alloy. End-chilled plates and cylindrical slugs of the composites were sand cast from above the liquidus temperature of the alloy. The cylindrical slugs were again reheated and used as starting material for die casting. Some of the reheated composites possessed “thixotropy.” Distribution of the ceramic particles in the alloy matrix was uniform in all the castings except for some settling of the coarse, 340ώ in size, particles in the end-chilled cast plates.     

High-Temperature Deformation Behavior and Formability of a Zr-Cu-Al-Ni Bulk Metallic Glass

The deformation behavior of a monolithic Zr₅₅Cu₃₀Al₁₀Ni₅ (at. pct) bulk metallic glass (BMG) fabricated by suction casting has been investigated at elevated temperatures in this study. A series of compression tests has been performed in the supercooled liquid temperature region. In the homogeneous flow regime, this alloy exhibited a transition from the Newtonian to non-Newtonian flow depending upon both the strain rate and the temperature. These two flow modes were then described by applying the Newtonian viscous flow theory and the transition state theory, respectively. On the basis of a dynamic materials model (DMM), a processing map could successfully be constructed to estimate the feasible forming conditions for this BMG alloy. Imaginary laboratory-scale extrusion tests were also performed to determine solid-to-solid formability, and the results from both the finite element method (FEM)-based simulation and processing map were then compared and discussed. This article is based on a presentation given in the symposium entitled “Bulk Metallic Glasses IV,” which occurred February 25–March 1, 2007 during the TMS Annual Meeting in Orlando, Florida under the auspices of the TMS/ASM Mechanical Behavior of Materials Committee.     

Synthesis and Characterization of Al–Mg–SiO<Subscript>2</Subscript> Particulate Composite Using Amorphous SiO<Subscript>2</Subscript> from Rice Husk Ash

This paper discusses the effect of the dispersion of amorphous nano size (35–55 nm) SiO₂ particles in Al–Mg (5%) alloy. Amorphous SiO₂ (>95% SiO₂) extracted from rice husk was added to the Al–Mg (5%) alloy in the proportion of 5 wt% of the Al–Mg alloy. The work aims to study the evolution of different phases like MgAl₂O₄, Mg₂Si, and MgO in Al–Mg–SiO₂ composite using amorphous nano SiO₂. Experimental results of the synthesized composite show presence of MgAl₂O₄ (Spinel structure) and other phases like MgO and Mg₂Si which impart hardness of 126.82 HV_10g to the composite. The Al–Mg (5%) SiO₂ composite microstructure appeared as a typical lamellar structure. The XRD and energy dispersive spectroscopy analysis display the presence of Mg₂Si formed along the grain boundary.     

Ion-plasma Ti-Al-N coatings on a cutting hard-alloy tool operating under conditions of constant and alternating-sign loads

Structure and phase formation during the deposition of coatings of the Ti-Al-Ni system (Al ≈ 3.5 at %) by the ion-plasma method are investigated. The controlled process parameter was the bias potential (U _b) applied to the substrate made of the VK6 hard alloy. At U _b = 120 V (samples of group 1), titanium nitride close to the stoichiometric composition and solid solution of Al in α-Ti are formed, while at U _b = 120 V (group 2), nonstoichiometric titanium nitride and complex nitride (Ti, Al)N are formed. The hardness and elasticity modulus for coatings of group 1 were equal to 23.8 GPa and 462 GPa, and for group 2 they were 30.8 GPa and 565 GPa, respectively. The latter are characterized by a level of adhesion strength of 53–55 N as opposed to 39–40 N for coatings of group 1. Qualification tests for the durability of the cutting tool with developed coatings are performed. For example, upon turning steel 45, it increases by a factor of 6.3 and for gray cast iron it increases by a factor of 5; during end milling cut of the EI 698-VD alloy it increases by a factor of 2.5.     

Foamability of MgAl2O4 (Spinel)-Reinforced Aluminum Alloy Composites

A novel foamable aluminum alloy has been developed. It contains sub-micron-sized MgAl₂O₄ (spinel) particles that are generated in situ by a reaction of SiO₂ with a molten Al-Mg alloy. The study involves an optimization of parameters such as Mg concentration, SiO₂ particles size, and reaction time and shows that a composite containing MgAl₂O₄ particles as chief reinforcement in the matrix leads to effective foaming. Composites containing large sized transition phases and particle agglomerates in the matrix yield poor foam structure. The best foamable composite obtained contained 3.4 vol. pct of ultrafine (80 nm to 1 μm) MgAl₂O₄ particles uniformly distributed in an Al-Si alloy matrix. The corresponding metal foam contained 75 pct porosity and exhibited a uniform distribution of cells.     

Structure and properties of multicomponent eutectic alloys based on chromium and titanium carbide

We have investigated alloys in the Cr-Mo-Ti-C, Cr-Re-Ti-C, and Cr-Mo-Re-Ti-C systems in the eutectic <Cr>+<TiC> crystallization region. We found a four component quasibinary eutectic <Cr, Mo>+<TiC> with 4–8 at. % molybdenum content with melting point 1630°C. Additions of 3–11 at. % Mo or 5–20 at. % Re to the base eutectic alloy Cr₇₉Ti₁₂C₉ doubles the Vickers hardness at 1000°C (to approximately 2000 MPa), and simultaneous introduction of molybdenum and rhenium (the alloy Cr₅₁Mo₈Re₂₀Ti₁₂C₉) raises the hardness to 3000–3500 MPa. Ukrainian Materials Science Institute, National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2, pp. 15–23, January–February, 1997.     

Aging processes in precipitation-hardening composite materials based on a D16 aluminum alloy

Aging of composite materials (CMs) based on an aluminum D16 alloy and reinforced by Al₃Ti intermetallic inclusions (0–10 vol %) having formed upon an in situ reaction and by SiC particles (0–30 vol %) ≤3 or 28 μm in size is studied. Oxide ceramic nanoparticles (0.1 wt %) are used to modify the structure of the CMs. The structures of the CMs before and after aging are analyzed by optical microscopy and scanning electron microscopy on a microscope equipped with an X-ray energy dispersive spectrometer. The hardness of the CMs is measured. The overall hardening of aged CMs is shown to result from a competition between the hardening effects induced by the formation of Guinier-Preston zones and the precipitation of the high-temperature θ and S phases. These effects are controlled by the dislocation density in the matrix.     

Behavior of a nickel-base high-temperature alloy under hot-working conditions

The behavior of a Ni-Cr-Co base alloy with significant additions of Mo, Ti and Al (Nimonic 105) under hot working conditions was studied using hot compression tests in the temperature range of 1223 to 1523 K and strain rates between 0.38 and 64.3 s^-1. The microstructure of the Nimonic 105 is complex and the matrix contains second phases in the form of Ni₃ (Ti, Al) dispersion (γ′), various Cr and Ti carbides and titanium cyanonitrides inclusions. However, the results show that above the dissolution temperature of the γ′ phase, the alloy behaves like a single phase nickel-base solid solution from the point view of steady state flow stress-temperature-strain rate relationships, and the activation energies for hot working and static recrystallization. Under deformation conditions where the γ′ phase is present, as in the case of creep, the activation energy is almost doubled. The hot working temperature range giving sound product is 1280 to 1450 K (170 K) at a strain rate of 0.4 s^-1 and decreases to 1400 to 1480 K (80 K) at a strain rate of 65 s^-1. At temperatures above the higher limit the alloy suffers intercrystalline cracks due to hot shortness and at temperatures below the lower limit the alloy suffers transcrystalline cracks due to excessive strain hardening.     

Erosion-resistant coatings for gas turbine compressor blades

The effect of ion-plasma coatings made from high-hardness metal compounds on the erosion and corrosion resistance and the mechanical properties of alloy (substrate) + coating compositions is comprehensively studied. The effects of the thickness, composition, deposition conditions, and design of coatings based on metal nitrides and carbides on the relative gas-abrasive wear of alloy + coating compositions in a gas-abrasive flux are analyzed. The flux contains quartz sand with an average fraction of 300–350 μm; the abrasive feed rate is 200 g/min; and the angles of flux incidence are 20° (tangential flow) and 70° (near-head-on attack flow). Alloy + coating compositions based on VN, VC, Cr₃C₂, ZrN, and TiN coatings 15–30 μ m thick or more are shown to have high erosion resistance. A detailed examination of the coatings with high erosion resistance demonstrates that a zirconium nitride coating is most appropriate for protecting gas turbine compressor blades made of titanium alloys; this coating does not decrease the fatigue strength of these alloys. A chromium carbide coating is the best coating for protecting compressor steel blades.     

Development and elemental powder metallurgy of a Y-containing two-phase TiAl alloy

The Y modification of a two-phase (γ+α ₂) TiAl-(Mn,Mo,C) alloy was studied with an aim to improve, mainly, the oxidation resistance and the mechanical properties in a high-temperature air environment. The experimental alloy was prepared by the elemental powder metallurgy (EPM) method. The addition of up to 0.6 at. pct Y resulted in a significant improvement in tensile properties and compressive yield strength and an anomalous yielding phenomenon withal. Two structural characteristics were identified: first, microstructural refinement in terms of the grain size as well as the interlamellar spacing, and second, precipitation of fine oxides that might scavenge harmful oxygen. Deformation was found to be mainly provided by 1/2<110] ordinary dislocations and a much lesser amount of <011] superdislocations as compared to what has been reported in other (γ+α ₂) TiAl alloys. The oxidation resistance of the experimental alloy was evaluated by air-exposure tests at 800 °C, from which the oxidation kinetics and the morphological and phase characteristics of the oxide scales were analyzed. With a Y addition, the constituents of the oxide scale changed from those of the Y-free alloy. In the case of the Y-free alloy, the oxide scale which formed upon extended air exposure (350 hours) at 800 °C consisted of a mixture of TiO₂ and α-Al₂O₃. In the case of the alloy modified with Y (0.6 at. pct), however, the oxide scale formed in an identical environment was considerably different: it consisted of a complex mixture of TiO₂, α-Al₂O₃, Y₂O₃, and Al₅Y₃O₁₂. The formation of the multiphase (Y,Al)O-rich oxide scale impedes the oxygen transport and the thermal-expansion stress in the Al₂O₃ layer. It is also suggested that a Y addition reduces the oxygen solubility and concentration of oxygen vacancices in the TiO₂ layer. This article is based on a presentation made in the symposium entitled “Fundamentals of Structural Intermetallics,” presented at the 2002 TMS Annual Meeting, February 21–27, 2002, in Seattle, Washington, under the auspices of the ASM and TMS Joint Committee on Mechanical Behavior of Materials.     

Structural superplasticity in a fine-grained eutectic intermetallic NiAl−Cr alloy

A rapidly solidified and thermomechanically processed fine-grained eutectic NiAl−Cr alloy of the composition Ni₃₃Al₃₃Cr₃₄ (at, pct) exhibits structural superplasticity in the temperature regime from 900°C to 1000°C at strain rates ranging from 10⁻⁵ to 10⁻³ s⁻¹. The material consists of a B2-ordered intermetallic NiAl(Cr) solid solution matrix containing a fine dispersion of bcc chromium. A high strain-rate-sensitivity exponent of m=0.55 was achieved in strain-rate-change tests at strain rates of about 10⁻⁴ s⁻¹. Maximum uniform elongations up to 350 pct engineering strain were recorded in superplastic strain to failure tests. Activation energy analysis of superplastic flow was performed in order to establish the diffusion-controlled dislocation accommodation process of grain boundary sliding. An activation energy of Q _c=288±15 kJ/mole was determined. This value is comparable with the activation energy of 290 kJ/mole for lattice diffusion of nickel and for ⁶³Ni tracer selfdiffusion in B2-ordered NiAl. The principal deformation mechanism of superplastic flow in this material is grain-boundary sliding accommodated by dislocation climb controlled by lattice diffusion, which is typical for class II solid-solution alloys. Failure in superplastically strained tensile samples of the fine-grained eutectic alloy occurred by cavitation formations along NiAl‖‖Cr interfaces.