Metal-intermetallic Laminate Research Articles

Continuous carbon fiber reinforced Ti/Al3Ti metal-intermetallic laminate (MIL) composites fabricated using ultrasonic consolidation assisted hot pressing sintering

A continuous carbon fiber reinforced Ti/Al3Ti metal-intermetallic laminate (Cf–Ti/Al3Ti MIL) composite was fabricated using an ultrasonic consolidation (UC) assisted hot pressing (HP) sintering technique. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were employed to characterize the microstructure of the UC-prepared laminate tapes (LT) and as-sintered Cf–Ti/Al3Ti MIL composite. The tensile and compressive mechanical properties of the Cf–Ti/Al3Ti MIL composites were measured. The results show that under a large normal force exerted by the sonotrode and severe transverse shear force transformed by the ultrasonic vibration, the Cf bundles could be separated into individual fibers and uniformly embedded into the Al foils surface layer without macroscopic defects. Using subsequent HP sintering, the Cf were successfully implanted into the Al3Ti matrix, and the mutual diffusion of the elements occurred between the fibers and the Al3Ti matrix, which indicated that the metallurgical bonding formed at the interface of the fiber/matrix during HP sintering. Furthermore, Cf–Ti/Al3Ti MIL composites exhibited better combinations of tensile and compressive properties than the MIL composite without the fiber reinforcement. The reinforcing mechanisms of the fibers are also discussed in detail.

Design, fabrication and characterization of FeAl-based metallic-intermetallic laminate (MIL) composites

FeAl-based MIL composites of various iron alloys were fabricated with an innovative “multiple-thin-foil” configuration and “two-stage reaction” strategy. Alternating stacked metal foils were reactive sintered via SPS at 600 °C and 1000 °C to grow intermetallics. The “multiple-thin-foil” configuration reduces reaction time, enables local chemical composition control and allows metal/intermetallic combinations, which cannot be produced via the conventional methods. Fe–FeAl, 430SS-FeAl, and 304SS-FeAl MIL composites can be synthesized with desired metallic/intermetallic ratios, where FeAl is the single intermetallic phase present in the composites. Microstructure analysis via SEM, EDS, and EBSD confirms phase identification and reveals the formation of transition layers. The transition layer, which incorporates the composition gradient between the metal (Fe, 430SS or 304SS) and the FeAl intermetallic phase, provides a gradual change in mechanical properties from the metal to intermetallic layers, and further functions as a chemical barrier into which other undesired intermetallics dissolve. Driven by diffusion-controlled growth, grains in the transition layers and FeAl regions exhibit ordered arrangement and sintering textures. Hardness profiles from the metal layer to FeAl region reveal the correlation between local mechanical properties and local chemical compositions. In compression testing, the compressive strength can reach 2.3 GPa with considerable plasticity, establishing the best mechanical properties of any MIL composites synthesized to date.

Fracture of metal-intermetallic laminate target under high-velocity impact

Deformation and fracture of laminates under high-velocity impact were numerically investigated. Targets consisting of alternating layers of intermetallide (Al3Ti) and titanium alloy (Ti-6Al-4V) were used as laminate composites. A high-strength steel core was used as a projectile. Impact velocities were varied in the range of 2000-5000 m/s. Fracture of intermetallic layers is described by the brittle fracture model, and fracture of titanium alloy layers is described by the active-type kinetic model. The erosion fracture model is used to simulate the fracture of the material under intensive deformation. The modified finite element method (without a global stiffness matrix) was used for numerical computations. It is revealed the increasing role of shock wave processes in the fracture of targets with increasing an impact velocity. The metal-intermetallic laminate target delaminates due to the fracture of intermetallic layers in shock waves and the formation of main cracks in these layers.

Numerical Simulation for Elasto-Plastic Contact of Novel Ti-(SiCf/Al3Ti)-Laminated Composite with Double-Layered SiC Fiber Reinforcements

An innovative, high-strength metal–intermetallic-laminate (MIL) composite Ti-(SiCf/Al3Ti), reinforced by double or even several SiC fiber rows, was fabricated. A high-efficiency, semi-analytical model with a numerical equivalent inclusion method (NEIM) was employed to investigate the deformation behaviors, microscopic strengthening, and failure mechanisms of the composite during elasto-plastic sphere–plane contact. The microstructure and interface features were characterized by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The contact model for the Ti-(SiCf/Al3Ti) composite was validated via quasi-static compressive indentation tests with a spherical indenter. A series of in-depth parametric studies were conducted to quantify the effect of the microstructure. The results indicate that the as-fabricated laminated composite has a well-organized microstructure and a higher volume fraction of fibers. The SiC fiber rows effectively enhance the strength and toughness of the composite. The optimal diameter of the SiC fibers is 32 μm when the horizontal center distance between the adjacent fibers is 2.5 times that of the fiber diameter. The hole defects occurring above the fibers would damage the material strength most compared with those occurring in other positions. The optimal quantity of the SiC fiber rows is four when the thickness of the SiCf/Al3Ti layer is 400 μm and the fiber diameter is 8 μm.

Explosion Welding: Process Evolution and Parameters Optimization

The development of explosion welding (EXW) technology underwent a stop as soon as it was introduced, however, in the recent years an increasing interest was found due to the wide range of materials which can be welded, similar and especially dissimilar ones. In addition to the high quality, such welded joints show a good compromise among the involved materials properties. Literature does not provide a comprehensive understanding of the whole mechanism and occurring phenomena but is mostly limited to analyse just some process parameters, like the investigations on joint properties that can be achieved if process takes place under vacuum or open air. In this work some key points are discussed to describe the evolution step of the process and the innovations introduced like the MIL (metallic-intermetallic laminate) composites for aerospace industry. Process parameters are analyzed to highlight the positive and negative aspects, the experiments in the laboratory will be described to confine the explosion to the joint and in particular to minimize the explosion energy and to improve the efficiency of the technique. At last some significant applications where this technique is widely used are showed.

Synthesis of MIL composites by various methods

Four methods such as thermal explosion, reactive sintering, reactive pressing, and explosive welding + sintering are considered for the obtaining of the Ti-TiAl3 metal-intermetallic laminate composite. The microstructure and phase composition of the samples are studied by the X-ray diffraction, local X-ray spectrum and optical microscopy methods. The study shows that multi-laminate composites can be obtained by all four methods.

Failure Mechanisms of Ti-Al3Ti metal-Intermetallic Laminate Composites Under High-Speed Impact

The penetration process of Ti-Al3Ti metal-intermetallic laminate composites impacted by a projectile was numerically investigated. The ballistic performance, stress distribution, failure and energy absorbing mechanisms of Ti-Al3Ti metal-intermetallic laminate composites under high-speed impact were examined in detail. The results show that Ti-Al3Ti metal-intermetallic laminate composites under high-speed impact is mostly under tensile stress, since the compressive wave is reflected back as a tensile wave. During projectile penetration, transverse, inclined, and vertical cracks are formed in the Al3Ti phase, which can dramatically absorb the kinetic energy of projectile.

A second order numerical scheme for the annealing of metal–intermetallic laminate composite: A ternary reaction system

Metal–Intermetallic Laminate (MIL) composites are laminate structures that are fabricated by optimizing unique benefits of constituent components to have attractive physical and mechanical features, such as high strength, stiffness, and toughness. The synthesis of MIL composites involves annealing reaction of multiple metallic elements at high temperatures. In this work, we propose, analyze, and implement a second-order semi-implicit scheme for the annealing of a ternary metallic reaction system. The robustness of such a numerical scheme is demonstrated by various numerical experiments, as well as the expected accuracy tests. At the theoretical level, we provide a detailed convergence analysis, which confirms the second-order accuracy in both the temporal and spatial discretization. Moreover, this numerical scheme is used to study the annealing process of the Al–Fe–Ni ternary system. The computation reproduces the formation of the Al-rich and Ni-rich layers in the annealing process. We present the computational results as diffusion paths in a ternary phase diagram, with a nice agreement with that of experimental data. We also study the growth kinetics of the two layers by calculating the rate constant and kinetic exponent of the reaction. The morphology of interfaces between different layers is thoroughly investigated as well. The computational results indicate that the numerical scheme is an effective, useful tool for predicting the microstructure evolution in the annealing process of a ternary reaction system.

Interface characteristics of Ti6Al4V-TiAl metal-intermetallic laminate (MIL) composites prepared by a novel hot-pack rolling

Ti6Al4V (wt%)/Ti-44Al-8Nb-0.2W-0.2B-0.03Y (at.%) (high Nb-TiAl) metal–intermetallic laminate (MIL) composite with a defect-free interface was successfully prepared by hot-pack rolling and the interface microstructure was characterized by XRD, SEM, EBSD, and TEM techniques. The results showed that the interface was about 260 μm thick and consisted of four different microstructure regions. The thickness of each region was about 60–80 μm and the microstructure of the four regions consisted of acicular O, α2, and β/B2 phases; acicular α2 phase; acicular α2 and β/B2 phases; and acicular γ, α2, and β/B2 phases respectively. The resulting microstructure of the interface region was attributed to the interdiffusion of Ti atoms from the starting Ti6Al4V alloy layer to the high Nb-TiAl alloy layer and Al and Nb atoms from the high Nb-TiAl alloy layer to the Ti6Al4V alloy layer. The formation of acicular α2 and γ phases was diffusion-controlled and the Nb segregation at the interface caused the formation of O phase which had specific relationships with α2 and β/B2 phases. The detailed interface microstructural evolution of the Ti6Al4V/high Nb-TiAl MIL composite and the Vickers hardness of the composite are also discussed in this paper.

Elasto-Plastic Mechanical Properties and Failure Mechanism of Innovative Ti-(SiCf/Al₃Ti) Laminated Composites for Sphere-Plane Contact at the Early Stage of Penetration Process.

A novel silicon carbide (SiC) continuous ceramic fiber-reinforced (CCFR) Ti/Al3Ti Metal-Intermetallic-Laminate (MIL) composite was fabricated. A high-efficiency semi-analytical model was proposed based on the numerical equivalent inclusion method (NEIM) for analyzing the small-strain elasto-plastic contact in the early stage of the penetration process. The microstructure and interface features were characterized by the scanning electron microscopy (SEM). Quasi-static compression tests were performed to determine the contact response and validate the proposed model. A group of in-depth parametric studies were carried out to quantify the influence of the microstructure. The comparison between results under the sphere-plane and plane-plane contact load indicates that, under the first sphere-plane, the compressive strength and failure strain are both lower and the SiC reinforcement effect on strength is very clear while the effect on ductility is not clear. The maximum plastic strain concentration (MPSC) in the Al3Ti layer is closest to the upper boundary of the central SiC fiber and then extends along the depth direction as the load increases, which are also the locations where cracks may initiate and extend. Moreover, the CCFR-MIL composite shows better mechanical properties when the center distance between adjacent SiC fibers is four times the fiber diameter and the volume fraction of Ti is 40%.

A Three-Dimensional Multi-scale Plasticity Model for Metal-Intermetallic Laminate Composites Containing Phases of the L12 Structure

A three-dimensional plasticity model was developed and applied to metal-intermetallic laminate composites containing phases of the L12 structure. A multi-scale approach that combined the methods of continuum mechanics and dislocation kinetics was used. This model takes account of the different mechanisms of self-locking superdislocations, the dislocations and the dislocation walls’ density storage for each type of layer at the micro-scale. At the meso-scale, the solutions to the dislocation kinetics equations, in the form of stress–strain curves, were used to create the properties of a three-dimensional representative element. The numerical simulation study of the macroscopic deformation was carried out with the finite element method using the dynamic model of continuum mechanics, which included the classical conservation laws, constitutive equations and the equation of state. It was shown that the simulation results generated using this model were in good agreement with the mechanical tests conducted on the single crystals of the L12 structure. The model provides an excellent description of the high-temperature plastic strain superlocalization effect of single crystal intermetallics of the L12 structure. This paper describes the numerical results of the study of the tension and compression tests of metal-intermetallic laminate composites containing phases of the L12 structure. The model allows the description of the distribution of the accumulated plastic strain inhomogeneities and is capable of predicting the strengthening properties and plastic behaviour of the metal-intermetallic laminate composites containing phases of the L12 structure.

Synthesis of metal-intermetallic laminate (MIL) composites with modified Al3Ti structure and in situ synchrotron X-ray diffraction analysis of sintering process

Al3Ti-based alloys attract exceptional attention due to their high specific mechanical properties. However, their application is still insufficient due to their low ductility and fracture toughness. Several approaches were previously proposed to address these problems. The first one is stabilization of the cubic modification of titanium trialuminide by alloying. Another approach consists in fabricating metal-intermetallic laminated composites (MIL). In this study, we combined both methods to synthesize the first MIL composite with cubic Al3Ti interlayers. Copper additions were used to stabilize the cubic modification of Al3Ti and produce a novel Ti-Al5CuTi2 MIL composite. First mechanical characterization by indentation tests showed that the binary Al3Ti intermetallic tended to crack at a load of 0.2 kg while the fracture was not observed in the Al5CuTi2 layers at least at a load of 1 kg. These results are an indirect evidence of a higher ductility and fracture toughness of the composite with cubic Al3Ti compared to tetragonal one. The sequence of the phase transformations in the Al-Ti-Cu system was studied using in situ synchrotron X-ray radiation diffraction. The formation of Al5CuTi2 occurred via several intermediate stages including eutectic melting of Al and Cu and the formation of binary AlCu and Al3Ti compounds.

Improved fracture toughness of NiTi shape memory alloy fiber-reinforced Ti-Al metal-intermetallic-laminate composite

In this paper, the fracture toughness of Ti-Al metal-intermetallic-laminate (MIL) composite with and without NiTi shape memory alloy fibers was comparatively investigated via a three-point bending test. The results indicated that the fracture toughness of the NiTi shape memory alloy fiber-reinforced (SMAFR) Ti-Al MIL composite was almost twice as much as that of the Ti-Al MIL composite without NiTi fibers. The improved toughness of the SMAFR MIL composites is mainly attributed to the plastic deformation and breakage of the NiTi fibers. In addition, the debonding of NiTi fibers, the repeated deflection of the main crack in the intermetallic layers, and the grain refinement of the intermetallic contribute to the toughening of the SMAFR MIL composite through absorption of energy.

Microstructure evolution in Ni and Ni-superalloy based metallic-intermetallic laminate (MIL) composites

Pure nickel and Nickel Alloy-X based Metallic-Intermetallic Laminate (MIL) composites were fabricated and investigated for their microstructure evolution, growth kinetics and microhardness distribution across the intermetallic/metal interfaces. Multi-phase layer structure with parabolic growth kinetics is shown in the nickel-based MIL composites. A two-phase eutectic layer along with a uniform layer form in the Alloy-X based MIL composites, which shows a mixed growth kinetic mechanism. The microhardness distribution across the intermetallic/metal interface of the two MIL composites was investigate with respect to the effects of texture and microstructure of the intermetallic phases. A simple intermetallic growth model is developed and validated for predicting the phase formation in binary or ternary reactions for synthesis of these MIL composites.

Microstructure evolution in pure Ni and Invar-based Metallic-Intermetallic Laminate (MIL) composites

Metallic-Intermetallic Laminate composites of Ni/Al and Invar/Al were fabricated and investigated for the microstructure evolution, growth kinetics and microhardness distribution across the intermetallic/metal interfaces. A single-phase intermetallic layer, with parabolic growth kinetics, is shown in the pure Ni/Al reaction, while a complex multi-phase layer (eutectic and uniform layer) with mixed growth kinetic mechanisms is identified in the Invar/Al reaction by EDS and EBSD analysis. Primary growth and texture of the intermetallic phase in Invar-based MIL are analyzed with respect to their effects on the microhardness distribution across the metal/intermetallic layer. The intermetallic yield rate of the two different Ni-aluminide reactions are calculated and demonstrated to be reliable for predicting the final intermetallic layer thickness in Ni-based MIL composites.

СИНТЕЗ МЕТАЛЛО-ИНТЕРМЕТАЛЛИДНОГО СЛОИСТОГО КОМПОЗИЦИОННОГО МАТЕРИАЛА СИСТЕМЫ Ti–TiAl3 РАЗЛИЧНЫМИ МЕТОДАМИ

СИНТЕЗ МЕТАЛЛО-ИНТЕРМЕТАЛЛИДНОГО СЛОИСТОГО КОМПОЗИЦИОННОГО МАТЕРИАЛА СИСТЕМЫ Ti–TiAl3 РАЗЛИЧНЫМИ МЕТОДАМИ

Work hardening behavior of Ti/Al-based metal intermetallic laminates

Titanium- and aluminum-based in situ metal intermetallic laminate (MIL) composites were prepared by solid-state diffusion bonding. The transition joints between Ti/Al were made at temperatures 550 and 575 °C with different bonding time under uniaxial pressure of 4 MPa under high vacuum to achieve MILs with different volume fraction of intermetallic phase. The phase and elemental analyses revealed the presence of only TiAl3 intermetallic layer formed between Ti/Al diffusion couple. Also, the layer thickness of the intermetallic phase increased with the increase in both bonding time and temperature. Compression tests were conducted on these MILs at room temperature both parallel and perpendicular to intermetallic layers. The mechanical properties and the failure mode of these MILs were studied based on the volume fraction of intermetallic phase. Results showed that the strength along the parallel direction of the MILs were much higher than the perpendicular direction. The failure mechanism of the MILs also varied based on the volume fraction of the intermetallic phases. Fractography revealed that with high intermetallic content, cracks were formed only on the intermetallic layer irrespective of loading direction. MILs containing intermetallic phase fraction exhibited better work hardening rate and the hardening rate behavior varied with the loading orientation.

The Kinetics of TiAl3 Formation in Explosively Welded Ti-Al Multilayers During Heat Treatment

Metallic-intermetallic laminate (MIL) composites, including Ti/TiAl3 composite, are promising materials for many applications, namely, in the aerospace industry. One method to produce Ti/TiAl3 laminate composite is to provide close attachment between desired number of titanium and aluminum plates, so that by applying heat and/or pressure, the formation of intermetallic phases between the layers becomes possible. In this work, explosive welding was used to make a strong bond between six alternative Ti and Al layers. The welded samples were annealed at three different temperatures: 903 K, 873 K, and 843 K (630 °C, 600 °C, and 570 °C) in ambient atmosphere, and the variation of the intermetallic layer thickness was used to study the growth kinetics. Microstructural investigations were carried out on the welded and annealed samples using optical microscopy and scanning electron microscopy equipped with energy-dispersive X-ray spectrometer (EDS). X-ray diffraction (XRD) technique was used to identify the formed intermetallic phases. It was found that at each temperature, two different mechanisms govern the process: reaction controlled and diffusion controlled. The calculated values of activation energies for reaction-controlled and diffusion-controlled mechanisms are 232.1 and 17.4 kJ, respectively.

Annealing effects on the microstructure and properties of an Fe-based Metallic-Intermetallic Laminate (MIL) composite

430SS MIL composites were initially fabricated under semi-solid reaction at 655°C and then annealed at high temperature (1000°C) to obtain the ductile Fe-rich intermetallic phases. The microstructure evolution and micro-hardness distribution across the intermetallic/metal interfaces were investigated, as well as the experimentally and computationally evaluating the growth kinetics of the Fe-rich intermetallic layers. A multilayer structure (namely Al-rich layer, Fe-rich layer and B2 phase layer) with a complex mix of intermetallic phases (FeAl2, Cr5Al8 and FeAl) form in the high temperature annealed 430SS MIL composites. The FeAl phase with a B2 structure formed in the intermetallic layer provides a more gradual transition of mechanical properties across the intermetallic/metal layer. The growth mechanism of the Fe-rich layer is interface controlled, while the growth of the B2 phase layer is diffusion controlled based on both the experimental and numerical analysis. A relationship between the processing-microstructure-properties of the MIL composites has been established and applied to predict and tailor the microhardness distribution across the multi-layered structure of the 430SS MIL composites.

Interface tensile and fracture behavior of the Ti/Al3Ti Metal-Intermetallic Laminate (MIL) composite under quasi-static and high strain rates

A novel specimen was designed to study the interface tensile behavior and fracture mechanism of the Ti/Al3Ti Metal-Intermetallic Laminate (MIL) composite under quasi-static and high strain rates. The experimental results indicated that the interface tensile strength of the Ti/Al3Ti MIL composite increases with increasing strain rate. The fracture mechanisms of the Ti/Al3Ti MIL composite are different under quasi-static (~0.001/s) and high strain (~300/s) rates. Generally, fracture only occurs in the interface under quasi-static tensile condition, while the fracture is also found in Al3Ti layer apart from the interface under high strain rate. The quasi-cleavage features are visible in the interface surface of Ti layer in both quasi-static and high strain rates. Moreover, large dimples are found in the fracture surface under high strain rate, and the tearing ridges are more than that under quasi-static strain rate. The brittle Al3Ti layers show an intergranular fracture behavior, along with minor transgranular fractures and secondary micro-crack formed in the grain boundary.