Metal-intermetallic Laminate Composites Research Articles

Compressive mechanical behavior of B2 FeAl-based metal-intermetallic laminate composites

Compressive mechanical behavior of B2 FeAl-based metal-intermetallic laminate composites

Effect of the Ti volume fraction on microstructure and mechanical properties of brick-and-mortar structure Ti/Al3Ti metal-intermetallic laminate composites

The brick-and-mortar biomimetic structure Ti/Al3Ti metal-intermetallic laminate (BMS-MIL) composites were prepared by vacuum hot pressing. BMS-MIL composites with various Ti volume fractions from 45–71% were obtained by controlling the high-temperature diffusion time of Al–Ti. The phase composition of the BMS-MIL composites was analyzed, and the influence of Ti volume fraction on the microstructure was quantitatively characterized. Quasi-static compression and three-point bending tests were carried out to study the mechanical properties and fracture mechanism of the BMS-MIL composites. The results indicated that, in BMS-MIL composites, Al3Ti appears as polygonal platelets, and Ti fills the gaps between the platelets. With decreasing Ti volume fraction, the size of Al3Ti platelets increased, the number of platelets decreased, and the aspect ratio of platelets first increased and then decreased. The decrease of Ti volume fraction leads to the decrease of mechanical properties of composites. However, as a reasonable and efficient material design strategy, the brick-and-mortar structure ensured that the specific strength of the BMS-MIL composites with load perpendicular to the layer remained stable, with specific strength maintained between 345 and 353 kN m/kg. The compression properties with load parallel to the layer are significantly affected by the platelet's aspect ratio. The sample with 65% volume fraction Ti exhibited the optimal strength, specific strength, and failure strain when compressed parallel to the layer, with a strength of 1347.3 MPa, specific strength of 330.2 kN m/kg, and a failure strain of 6.32%.

Microstructure and mechanical properties of highly biomimetic brick-and-mortar structure Ti6Al4V/Al3Ti metal-intermetallic laminate composite

The brick-and-mortar structure of shell nacre allows for the simultaneous enhancement of strength and plasticity through the synergistic effect of multiple toughening mechanisms at different scales. In this work, a novel nacre-like brick-and-mortar structure Ti6Al4V/Al3Ti metal-intermetallic laminate (BMS-MIL) composite was successfully fabricated via vacuum hot pressing sintering method. The BMS-MIL composite is mainly composed of Al3Ti and Ti phases, with a small amount of Al2Ti and AlTi phases. Al3Ti is in the shape of polygonal platelet, and a 5–8 μm diffusion layer composed of Al2Ti and AlTi is distributed on the surface of the platelets. Ti6Al4V connects the platelets and is present in a continuous network frame structure. Compared with the layered structure Ti6Al4V/Al3Ti metal-intermetallic laminate (LS-MIL) composite, the fracture strain of BMS-MIL composite increases by 125.1% while maintaining high strength under load perpendicular to layer, and the compressive strength of BMS-MIL composite increases by 26.3% under load parallel to layer, respectively. Material isotropy in compressive properties has been significantly improved. In bending tests, the strength of the BMS-MIL composite is 1.9 times that of the LS-MIL composite. The brick-and-mortar structure’s excellent strengthening and toughening effect benefits from the enhancement of its crack constraint.

Microstructure characterization and mechanical properties of the 304SS-(NiTif/FeAl) metal-intermetallic laminate composites

In this work, a novel continuous NiTi Shape Memory Alloy Fiber Reinforced (SMAFR) B2-FeAl based metal-intermetallic laminate (MIL) composite was prepared via two-step vacuum hot pressing combined with “multi-thin foils” stacking configuration. The microstructure characterization of the composite was conducted by using X-ray diffractometer, scanning electron microscopy, electron backscattered diffraction and transmission electron microscopy. The compressive and tensile properties of the composites were measured. Results indicated that the SMAFR MIL composite exhibits multi-layer structure consisting of residual stainless steel layer, newly-formed intermetallic layer and intermediate transition layer. The intermetallic layer is composed of several sublayers with the boundaries of centerlines, and B2-FeAl phase is the main phase in this layer. NiTi fibers locate at the centerlines in the intermetallic layer and show a uniform distribution. A metallurgical interfacial bonding between NiTi fiber and FeAl matrix was obtained through the inter-diffusion of Ni, Ti and Al elements across the interface. In the intermediate transition layer, B2 phase was also the dominant phase, and a large amount of fine Al-rich precipitates dispersed in the matrix. Compared with the MIL composite without NiTi fibers, the SMAFR MIL composite possesses superior compressive and tensile properties, which are mainly attributed to (Ⅰ) high tensile properties of NiTi fiber, (Ⅱ) a good interfacial bonding of NiTi/B2-FeAl, (Ⅲ) strong interfacial reaction products, and (Ⅳ) pullout effect of NiTi fibers.

Ti-Al3Ti metal-intermetallic laminate (MIL) composite with a cubic titanium trialuminide stabilized with silver: Selection of fabrication regimes, structure, and properties

Ti-Al 3 Ti metal-intermetallic laminate (MIL) composites are known as promising structural materials due to the unique combination of their specific properties. However, their application is still limited due to the extremely high brittleness of the Al 3 Ti phase. In this study, we attempt to address this issue by changing the D0 22 crystal structure of Al 3 Ti to the more ductile L1 2 structure by alloying it with silver. To select the best fabrication regimes of Ti-Ti(Al 1−x Ag x ) 3 composites, in situ synchrotron X-ray diffraction analysis was performed to reveal the chemical reactions occurring upon heating the Ti-Al-Ag sample. The analysis showed that the highest amount of Ti(Al 1−x Ag x ) 3 phase with the L1 2 structure appears at 930 °C. This temperature was chosen for subsequent spark plasma sintering experiments. Scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction analysis revealed that the sintered sample consisted mainly of Ti, Ti(Al 1−x Ag x ) 3 , and a minor fraction of the Ag-Al compound distributed in the central parts of the intermetallic layers and at the grain boundaries. Modification of the titanium trialuminide crystal structure positively affected the properties of the composite, providing a 60% increase in fracture toughness. The Ag-Al phase also contributed to toughening, causing an additional crack deflection effect. • Ag stabilizes L1 2 crystal structure of Al 3 Ti in Ti-Al 3 Ti multilayer composite. • The maximum fraction of L1 2 phase in the composite is reached at 930 °C. • Modification of the Al 3 Ti provides 60% increase of the composite fracture toughness. • Minor Al-Ag phase causes the additional crack deflection effect.

Study on interface and mechanical properties of Ti–Al3Ti metal-intermetallic laminate reinforced by Ni-plated woven carbon fibers

Ni plated continuous woven carbon fibers (Ni–Cf) reinforced Ti–Al3Ti metal-intermetallic laminate composites (Ni-CfR-MIL) were prepared by electroplating assisted hot pressing sintering (HP). Scanning electron microscopy (SEM) was used to characterize the effect of Ni plating on the Cf surface, structure and interface of the composites. The diffusion distribution of elements was observed by using electron probe microscope analyser (EPMA) and energy dispersive spectrometer (EDS). Transmission electron microscopy (TEM) was used to observe and calibrate the interface in nanometer scale. The experimental results show that the interior of Cf bundle is completely infiltrated by Al. The Ni plating can promote the infiltration between Al and Cf, inhibit the interface reaction between Al and C, reduce the formation of harmful phase Al4C3 at the interface, and improve the bonding strength of Cf and matrix. There are diffusion layer I(Al3Ti) and diffusion layer II(Al13Fe4 & Al3Ni) in the material. Al4C3, Al13Fe4 and Al3Ni phases are formed by interfacial reaction during HP, and diffusion phase Al3Ni is precipitated in the Al3Ti layer near Ti layer. The tensile strength of Ni-CfR-MIL is 596Mpa and the fracture strain is 8.94%, both of which are better than that of Ti–Al3Ti MIL without fiber. The bending strength of Ni-CfR-MIL reaches 1101Mpa and the failure strain is 2.33%, which are 3.2 times and 1.9 times that of Ti–Al3Ti MIL respectively. By observing the crack of the failure fracture, the cause of performance improvement was analyzed.

Microstructures and Properties of AlMgTi-Based Metal-Intermetallic Laminate Composites by Dual-Steps Vacuum Hot Pressing.

AlMgTi-based metal–intermetallic laminated composites were successfully fabricated through an innovative dual-step vacuum hot pressing. First, this study prepares the AlTi-based laminated composites by vacuum hot pressing at 650 °C. Then, the researchers place the Mg-Al-1Zn (AZ31) magnesium alloy between the prepared AlTi-based laminated composites at 430 °C for hot pressing. This study investigates the microstructure, phase composition, and microhardness distribution across interfaces of the intermetallics and metal. A multilayer phase (Mg17Al12, Al3Mg2, and transition layers) structure can be found from the diffusion layers between Al and AZ31. The microhardness of the material presents a wavy distribution in the direction perpendicular to the layers; the maximum can be up to 600.0 HV0.2 with a minimum of 28.7 HV0.2 The microhardness gradient of an AlMgTi-based composite is smoother due to the different microhardness of the layers, and reduces the interface stress concentration. The bending strength of AlMgTi-based composites can reach 265 MPa, and the specific strength is 105 × 103 Nm/kg, higher than AlTi-based composites.

The effect of oxides on Fe/Al interfacial reaction in Metal-Intermetallic Laminate (MIL) composites

When fabricating Metal-Intermetallic Laminate (MIL) composites by hot pressing alternately stacked Al and Fe-based foils, the oxides on the surface of the sheets will affect the nucleation and growth kinetics of the intermetallic phases. The influence of the oxide surface layers on phase formation, growth kinetics and morphology of the intermetallic layer was studied by tracking the evolution of the initial oxide layer during interfacial reaction processing. The dominant intermetallic phase formed in the pure Fe/Al reaction was Fe2Al5 phase which preferentially grew along the dense packed direction of its unit cell ([001] direction in c-axis). In the early reaction stage, the morphology of aluminide growth is planar due to primarily two-dimensional diffusion. In the later stage of reaction, three-dimensional diffusion causes anisotropic growth of intermetallic layer with tongue-like morphology. The presence of the oxide layer also increases the growth rate of Kirkendall voids in the intermetallic phase.

Effect of residual stresses on the mechanical properties of Ti-TiAl laminate composites fabricated by hot-pack rolling

The Ti-TiAl laminate composites with different titanium alloy volume fraction were successfully designed and fabricated by hot-pack rolling. Due to the mismatch of coefficient of thermal expansion (CTE), the composites show pronounced residual stresses. The TiAl alloy possesses residual tensile stress while the titanium alloy possesses residual compressive stress. With the increase of titanium alloy volume fraction, the residual compressive stress is decreased but the residual tensile stress is opposite. The residual compressive stress is beneficial for improving the mechanical properties of Ti-TiAl laminate composites, which is because it enhances the strength and postpones the rupture of composites during tensile test. The higher residual compressive stress also improves the fracture toughness of composites by extending crack propagation. The composite with 42 vol% titanium alloy shows the optimal comprehensive mechanical properties, which is higher than most of other Ti-Al based metal-intermetallic laminate composites.

Microstructure characteristics of a high-entropy-alloy intermetallic laminate composite

The multi-principal elements CoCrFeNi/aluminide high-entropy-alloy intermetallic laminate composites (HILC) was prepared by solid diffusion welding method. The results showed that three intermetallics layers formed between CoCrFeNi and Al sheets. The intermetallic phases in the layers were identified to be Al5(FeCoCrNi)2 multi-principal elements ordered solid solution, Al13(FeCoNiCr)4 ordered solid solution, and Al13(FeCoNi)4 ordered solid solution + Al13Cr2 intermetallics, respectively. The hardness of intermetallic layers was much higher than that of CoCrFeNi alloy, which obeyed the design concept of metal-intermetallic laminate composites (MILC). The research and development of HILC broadened the MILC family.

Enhanced tensile strength and fracture toughness of a Ti-TiAl metal-intermetallic laminate (MIL) composite

High temperature titanium alloy/Ti-43Al-9V metal-intermetallic laminate composite was successfully fabricated by hot-pack rolling. The titanium alloy exhibits a lamellar structure and the TiAl alloy consists of B2 phase and elongated γ phase. Due to the low rolling and annealing temperature, the TiAl alloy shows a low extent of dynamic recrystallization (69.3%) and a high dislocations density (17%). The composite shows an excellent combination of the enhanced tensile strength and fracture toughness. The tensile strength of composite at 25 °C and 700 °C are 845 MPa and 730 MPa respectively. The fracture toughness of composite are 29.4 MPa∙m1/2 and 26.6 MPa∙m1/2 in arrester orientation and divider orientation respectively, which are much higher than monolithic Ti-43Al-9V alloy. The strengthening of composite is mainly attributed to high density dislocations and sub-structures stored in composite and the toughening mechanisms of composite are crack deflection, secondary cracks and crack tip convolution.

The mechanical performance and a rate-dependent constitutive model for Al3Ti compound

The Al3Ti compound has potential application in the high temperature structure materials due to its low density, high strength and stiffness. The mechanical behaviors of the material under different loading rates were studied using compression tests. The results indicate that Al3Ti is a typical brittle material and its compressive strength is dependent on the strain rate. Therefore, a series of rate-dependent constitutive equations are needed to describe its mechanical behaviors accurately. However, it is still short of professional research on the material model for Al3Ti. In this study, the material model was developed on the basis of JH-2 constitutive equations using the experimental data. The model was then applied in simulating the impact process of Ti/Al3Ti metal-intermetallic laminate composites so as to validate the established model. Good agreement between simulation and experiment results shows the constitutive model predict the material responses under high rate and large deformation accurately. This work provides more support for the theoretical and numerical research on the intermetallic.

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.

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.

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.