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In this paper, B2-FeAl based metal-intermetallic laminate (MIL) composites with and without NiTi shape memory alloy fibers were fabricated by two-step vacuum hot pressing combined with "multi-thin foils" stacking configuration. The microstructure of the composites were studied by scanning electron microscopy and electron backscattered diffraction. Compressive mechanical properties of the composites under quasi-static conditions and high strain rates are investigated via an Instron 5500R load frame and a Split Hopkinson Pressure Bar, respectively. Quasi-static compression stress–strain curves under the strain rate of 10–3/s at 20 °C and dynamic stress–strain curves under the strain rates of 1500/s and 2500/s at 0 °C, 20 °C and 80 °C were obtained, and fracture behavior of the composites were analyzed. The experimental results indicated that the strengths of the composites decreased unexpectedly under high strain rates compared to that under quasi-static condition whether or not NiTi fibers were introduced. Partial phase transition from austenite to ferrite occurred in metal layer during either quasi-static or dynamic compression process. During quasi-static compression, deformation was mainly concentrated in the metal layer. By contrast, metal layers and intermetallic layers exhibit similar deformation capacity during the dynamic loading process, thus, cracks easily appeared in intermetallic layers, causing the premature failure of the composites. Even so, B2-FeAl based MIL composites still possess the best dynamic mechanical properties in the MIL composites family to date. The strength of NiTi fiber reinforced composite is basically higher than that of the counterpart without NiTi fibers at each testing temperature, and fewer microcracks appeared in the intermetallic layer of the former. The reinforcing mechanism was discussed in details. [ABSTRACT FROM AUTHOR]

A novel method of preparing continuous NiTif‐reinforced Ti/Al‐laminated composites is proposed via ultrasonic consolidation (UC) and vacuum hot pressing. The microstructure of the composites is characterized by X‐ray diffraction, scanning electron microscopy, and electron backscattering diffraction. The tensile properties of the composites are measured by a universal testing machine. Results indicate that the composite exhibits multilayer structure consisting of residual NiTi fiber, intermetallic compounds (IMCs) layer, reaction layer, Ti layer, and Al layer. The intermetallic layer is composed of Al3Ti and Al3Ni, and some Ni‐rich precipitates are dispersed in the matrix. And with the introduction of UC assisted, grain refinement occurs at the IMC/Al interface, texture variation emerges at the NiTi fiber/IMCs interface, and a weakening of texture strength is observed at both interfaces. Compared to NiTif‐reinforced Ti/Al‐laminated composites without UC assisted, both the tensile strength (from 872.4 to 826.5 MPa) and failure strain (from 17.5% to 20.4%) of NiTif‐reinforced Ti/Al‐laminated composites with UC assisted increase due to the contribution of UC assisted. The reinforcing and fracture mechanisms of the UC assisted are also discussed. [ABSTRACT FROM AUTHOR]

A novel Shape Memory Alloy NiTi fiber-reinforced metal-intermetallic–laminate (SMAFR-MIL) composite with a volume fraction of ~ 3.5% NiTi was fabricated using vacuum hot pressing method in this paper. The microstructure characterization of this laminate composite was performed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD), and the mechanical property of SMAFR-MIL composite was determined by compression test. In addition, damping capacity was measured using Dynamic Mechanical Analyzer (DMA) in a temperature range from 30 °C to 50 °C. The experimental results indicated that the average compressive strength and the strain to failure are ~ 1208 MPa and ~ 4.4% for loading perpendicular to the layers, and ~ 962 MPa and ~ 4.8% for loading parallel to the layers, respectively. The loss modulus of SMAFR-MIL composite is ~ 3.7 GPa, which is five times greater than that of Ti/Al 3 Ti laminate composite without NiTi fiber reinforcement, while the damping factor of SMAFR-MIL composite is ~ 4.5%. Both the mechanical and damping tests demonstrated that SMAFR-MIL composite is a new class of structural and functional composite with superior mechanical and damping properties. [ABSTRACT FROM AUTHOR]

To improve the ductility of Al 3 Ti alloy, the continuous shape memory alloy NiTi fiber (CSMAR) was introduced into intermetallic Al 3 Ti matrix for fabricating the novel CSMAR-Al 3 Ti composite in this work. Microstructure characterizations demonstrated that the CSMAR-Al 3 Ti composite mainly consists of Al 3 Ti layer, NiTi fiber, eutectic area and interfacial reaction layer. EBSD results indicated that the eutectic area is made up of Al 3 Ti and Al 3 Ni phases, the Al 3 Ti phase shows a strong [001] crystallographic oriented structure, while the Al 3 Ni phase has a non-textured structure. TEM results showed that the interfacial reaction layer between NiTi fiber and eutectic area is a multiple phase mixture, including various Ti-Al and Ni-Al intermetallics. Furthermore, TEM and HRTEM analyses revealed a newly formed Ti 2 Ni layer between NiTi fiber and interfacial reaction layer. Tensile test results confirmed that the CSMAR-Al 3 Ti composite could effectively improve the ductility of the Al 3 Ti alloy. Based on the systematic investigations of interfacial microstructure characterization, mechanical behavior and fracture morphology observation, it is found that the toughening mechanism of CSMAR-Al 3 Ti composite is related to the interfacial fine grain strengthening effect with the gradual distribution characteristic. In addition, the excellent metallurgical bonding between fiber reinforcement and matrix is also beneficial to the mechanical properties. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this work, shape memory alloy NiTi fiber reinforced (SMAFR) Ti-Al laminated composites containing ∼41 vol%Ti and ∼2.5 vol%NiTi was fabricated via vacuum hot pressing method. In order to accurately determine the reaction products of the fabrication process, a new kind of laminated composites i.e. shape memory alloy NiTi plate-reinforced (SMAPR) Ti-Al laminated composites was successfully prepared using the fabrication process that is similar to SMAFR laminated composites. Results showed that Al 3 Ti and Al 3 Ni are formed during fabrication process, and residual Al existed in the intermetallic layer. In addition, the quasi-static tensile test indicates that the tensile property of SMAFR laminated composites is superior to that of Ti/Al 3 Ti composites. The fracture process of SMAFR laminated composite includes three basic stages: (I) delamination of interface of Ti/Al 3 Ti; (II) fracture of Al 3 Ti (and other products) and (III) fracture of NiTi fiber. Moreover, the novel SMAPR laminated composite possessed a good combination of high strength (compressive strength: 1105.4 MPa) and high plasticity (strain to failure: 5.1%), indicating that this kind of laminated composites is a new class of structural materials. [ABSTRACT FROM AUTHOR]

In this paper, a novel NiTi shape memory alloy fiber reinforced Mg3AlZn (SMAFR-AZ31) composite sheet was successfully fabricated by laminate structure design combined with hot pressing method using Mg3AlZn (AZ31) foils and continuous NiTi shape memory alloy fibers. The interfacial microstructure of the SMAFR-AZ31 composite sheet was systematically characterized by a high resolution transmission electron microscopy (FEI-TEM Talos F100) combined with an FEI Helios 600i focused ion beam/scanning electron microscopy (FIB/SEM) system. The normal tensile strength of the SMAFR-AZ31 composite sheet was tested using a novel direct tensile sample configuration with the tensile direction perpendicular to prior AZ31 foils. Results showed that a well-densified AZ31 matrix and uniformly distributed NiTi fiber reinforcements were obtained in the SMAFR-AZ31 composite sheet after hot pressing. A continuous interfacial reaction layer consisting of nanocrystalline-amorphous mixture and a few intermetallic phases were formed around the NiTi f /AZ31 interface. The nanocrystalline was identified as dual phase coexistence grains of MgO and TiO 2 , and the amorphous phase was a mixture of Mg–Ti–O and Mg–O. A newly Ti 2 Ni intermetallic phase that obeys a specific orientation relationship with NiTi fiber ([ 4 ‾ 2 1 ‾ ] NiTi// [ 1 ‾ 12 ] Ti 2 Ni, (132) NiTi// (1 1 ‾ 1) Ti 2 Ni with an angle difference of 6.27°) precipitated adjacent to the interface reaction layer. A Ni-rich intermetallic phase identified as AlNi formed at the NiTi f /AZ31 interface. Furthermore, it is found that large plastic deformation occurred near the interface reaction region in the AZ31 matrix, which is responsible for the successful embedding of NiTi fibers. Compared with the AZ31 laminate sheet without NiTi fibers, the SMAFR-AZ31 composite sheet possessed a superior normal tensile strength, which is attributed to the formation of the amorphous phase at the NiTi f /AZ31 interface. [ABSTRACT FROM AUTHOR]