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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]

Effects of electropulsing treatment (EPT) on the microstructure evolution, mechanical properties and crack healing of intermetallic Al 3 Ti alloys were studied in this work. In order to investigate the athermal effect caused by EPT, conventional heat treatment (CHT) was conducted for comparison. The compressive stress-strain curves demonstrated that the failure strains of Al 3 Ti alloy increase under both the EPT and CHT conditions, while the increment of failure strain of Al 3 Ti alloy treated by EPT is higher than that treated by CHT. Fracture surface analysis confirmed that the intrinsic brittle fracture of Al 3 Ti alloy evolves into the quasi-cleavage fracture with increasing frequency of EPT. Based on the systematic investigation into the microstructure evolution, mechanical properties and fracture surface observation, the influence mechanism of EPT on Al 3 Ti alloy was found to be related to the improvements of atomic diffusion and dislocation movement, which results from the coupling of thermal effect and athermal effect by EPT. Furthermore, the thermal compressive stress and athermal effect could heal the local micro-crack and decrease the crack width of Al 3 Ti alloy by EPT. Therefore, EPT can work as a novel method for improving the plastic deformation capacity of Al 3 Ti alloy. [ABSTRACT FROM AUTHOR]

A novel specimen was designed to study the interface tensile behavior and fracture mechanism of the Ti/Al 3 Ti Metal-Intermetallic Laminate (MIL) composite under quasi-static and high strain rates. The experimental results indicated that the interface tensile strength of the Ti/Al 3 Ti MIL composite increases with increasing strain rate. The fracture mechanisms of the Ti/Al 3 Ti 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 Al 3 Ti 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 Al 3 Ti layers show an intergranular fracture behavior, along with minor transgranular fractures and secondary micro-crack formed in the grain boundary. [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]

Ti/Al 3 Ti metal-intermetallic laminate (MIL) composite is fabricated using Ti and Al foils through the vacuum sintering process. The fracture behavior of the MIL laminate composite under dynamic loading is investigated via modified Hopkinson bar loaded three-point bending fracture test. An experimental–numerical hybrid method is used to simulate the fracture behavior of MIL composite. In this method, the brittle damage model and plastic kinematic model are employed to represent the dynamic responses of the brittle intermetallic matrix Al 3 Ti and ductile reinforcement of Ti, respectively. As the boundary condition, displacement data obtained from dynamic three-point bending fracture test are imported into the finite element software package for simulation. Finite element model is validated through the comparison of the load–displacement curves from numerical simulation and the Hopkinson bar loaded three-point bending test. In addition, the dynamic damage evolution behaviors of the laminate composite, including crack deflection, delamination, plastic deformation, and brittle fracture are investigated using the post-process technique of finite element software package. The current study demonstrates that the MIL composite has excellent damage tolerance due to the multiple energy-absorbing mechanisms. [ABSTRACT FROM AUTHOR]

The innovative Ti-(SiC f /Al 3 Ti) ceramic-fiber-reinforced metal-intermetallic-laminated (CFR-MIL) composites were successfully fabricated by vacuum hot pressing using titanium foils, aluminum foils and SiC ceramic fibers. The synthesized Ti-(SiC f /Al 3 Ti) composite showed a unique multilayered microstructure consisting of alternating SiC f /Al 3 Ti composite layers (SiC fiber as reinforcement) and Ti layers. In addition, reaction annealing technique was employed to improve the interfacial performance of SiC fiber with Al 3 Ti matrix. The microstructure evolution of the laminated composite during hot-pressing and annealing was experimentally characterized using scanning electron microscopy and energy dispersive spectroscopy. The formation mechanism of micro-laminated structure was discussed. Furthermore, the mechanical properties of the Ti-(SiC f /Al 3 Ti) laminated composite and its components were investigated by tensile and nanoindentation tests. The results indicated that Ti-(SiC f /Al 3 Ti) laminated composite exhibited superior mechanical properties compared to Ti-Al 3 Ti, which was likely attributed to the introduction of SiC fiber. The failure mechanism of CFR-MIL composite was the combined fracture behaviors of ductile fracture of Ti, brittle fracture of Al 3 Ti and fiber debonding, pullout and breakage of SiC. [ABSTRACT FROM AUTHOR]

In this work, TC4 coating was prepared on 45 steel surface successfully by laser cladding and Al 0.5 CoCrFeNi high-entropy alloys (HEA) coating was designed as an intermediate layer. Microstructure, microhardness and electrochemical corrosion characteristics of TC4/HEA composite coating were evaluated in detail. The interfaces without cracks of HEA layer/substrate and TC4 layer/HEA layer are clear and straight, and a metallurgical bonding is obtained when the line energy density is 315 J/mm2 and 180 J/mm2. A reactive layer consisted of Ti Al and Ti Fe intermetallic compounds (IMC) is formed at TC4/HEA interface. The HEA transition layers are composed of uniformly distributed equiaxed matrix (FCC) and intercrystalline phase (BCC), while a transition from Widmanstätten structure to coarse acicular crystal was found in TC4 layer. The microhardness of HEA coating is slightly higher than the substrate and lower than the TC4 coating, and the microhardness value of TC4 layer is up to 745.8 HV0.2. Potential dynamic polarization curves test results show that a comparatively small corrosion zone is concluded for TC4/HEA composite coating sample and the corrosion resistance of the composite coating is significantly improved with an increased value of 55.9 % in E corr (−0.325 V) and a decreased value of 99.3 % in I corr (0.1 μA/cm2) compared to the substrate. • TC4 coating with Al0.5CoCrFeNi HEA interlayer was prepared on 45 steel surface. • The undesirable Ti Fe intermetallic compounds at TC4/substrate interface was refrained. • The TC4 coatings exhibit excellent corrosion property than 45 steel substrate. [ABSTRACT FROM AUTHOR]

In this work, to improve the ductility of Al 3 Ti alloy, a multi-phase intermetallic mixture structure was achieved by the post annealing treatments (AT) on the as-fabricated continuous shape memory alloy NiTi fiber reinforced Al 3 Ti composite (CSMAR-Al 3 Ti). Experimental results revealed that the multi-phase intermetallic mixture structure displays a multi-layer characteristic, including the newly formed intermetallic layer and the eutectic area. Microstructure characterization and formation mechanism confirmed that the newly formed intermetallic layer consists of NiAl, Al 3 Ni 2 and Al 3 Ti phases, and the eutectic area still consists of Al 3 Ni and Al 3 Ti phases. The results of compression and tensile tests indicated that the multi-phase intermetallic mixture structure can simultaneously improve the maximum strength and the failure strain of the monolith Al 3 Ti alloy. Based on the systematic investigations, it is found that the toughening mechanism is related to the multi-layer characteristic of the multi-phase intermetallic mixture structure, which is beneficial to the crack blunting, crack deflecting and load transformation during the deformation process. Furthermore, the multi-phase intermetallic mixture structure achieved by the 48 h post annealing treatment is the most effective method to improve the ductility of Al 3 Ti alloy. [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]

The bulk titanium tri-aluminide intermetallic alloy was fabricated via foil reactive sintering using Ti and Al foils in the vacuum. Scanning electron microscopy (SEM) results demonstrated that the original Ti and Al foils were fully reacted and the only synthesized product is monolithic intermetallic Al 3 Ti. The basic physical properties of the fabricated intermetallic, such as Young's modulus and Poisson ratio, were determined using an ultrasonic wave measurement technique, and the compressive mechanical responses under both quasi-static and high strain rates were studied using universal load frame and modified split Hopkinson pressure bar system, respectively. The experimental results indicated that intermetallic Al 3 Ti exhibits brittle features, and its compressive strength was sensitive to strain rate. Moreover, the strain rate hardening behavior under high rate range is stronger than that under quasi-static deformation conditions. [ABSTRACT FROM AUTHOR]

Continuous Al 2 O 3 ceramic fiber reinforced Ti/Al 3 Ti metal-intermetallic laminated (CCFR-MIL) composite was fabricated using a vacuum hot pressing (VHP) sintering method and followed by hot isostatic pressing (HIP). The microstructure characteristics of the interfaces between Ti and Al 3 Ti, as well as Al 2 O 3 fiber and Al 3 Ti intermetallic were analyzed by scanning electron microscopy (SEM). Elemental distribution in the interfacial reaction zones were quantitatively examined by energy-dispersive spectroscopy (EDS). The phases in the composite were identified by X-ray diffractometer (XRD). The mechanical properties of the CCFR-MIL composite were measured using compression and tensile tests under quasi-static strain rate. The experimental results indicated that the residual Al was found in Al 3 Ti intermetallic layer of CCFR-MIL composite. The interfacial reactions occurred during HIP and the reaction products were determined to be Al 2 Ti, TiSi 2 , TiO 2 and Al 2 SiO 5 phases. Compared to Ti/Al 3 Ti MIL composite without fiber reinforcement, both the strength and failure strain of CCFR-MIL composite under both compressive and tensile stress states increased due to the contribution of the continuous ceramic Al 2 O 3 fiber. [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]

Intermetallic Al 3 Ti alloys with different volume fractions of residual aluminum were synthesized via reactive foil sintering in vacuum condition using commercial purity aluminum foils and Ti-6Al-4V alloy foils. Microstructure evolution, elemental analysis, fracture mechanism and phase identification were performed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) technique, respectively. Mechanical properties were measured by quasi-static compression and Vickers hardness tests. Experimental results indicated that the ductile phase Al distributes in the grain boundaries of the brittle matrix Al 3 Ti, which increases the compression failure strain of the Al 3 Ti alloy dramatically compared with the monolithic intermetallic Al 3 Ti alloy. The compressive stress-strain curve showed a typical elastic-plastic deformation behavior. Moreover, it also demonstrated that the post-heat treatment plays an important role in the mechanical properties due to the formation of α-Al 2 O 3 and Al 3 Ti grain coarsening. [ABSTRACT FROM AUTHOR]