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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 layered structure reinforced composite metal foam was fabricated using metal fiber grids by casting method. • The layered structure can greatly improve the compression performance of the CMF. • The deformation mechanism of composite metal foam and layered structure reinforced composite metal foam was discussed. The composite metal foam was focused on the shear deformation, while that of the layered structure reinforced composite metal foam was the cylinder deformation with the deformation occurring layer by layer. The layered structure reinforced composite metal foam (LS-CMF) was designed and fabricated using metal fiber grids (MFGs), 316 L stainless steel hollow spheres (MHSs), and A356 aluminum alloy through the casting method. Afterwards, the physical parameters, microstructure and compression performance of the LS-CMF were characterized. The results reveal that the density of the LS-CMF is 1.99 ± 0.06 g/cm3. The MHSs and metal fiber combined well with the matrix and formed the transition layer. The transition layer of single-layer structure between the MHSs and the matrix was composed by Fe 2 Al 7 Si phases, while, the transition layer between the metal fiber and the matrix was a three-layer structure composed by Fe 2 Al 7 Si, Fe 25 Al 60 Si 15 and Fe phases. Besides, the compression results prove that the layered structure can increase the average stress plateau strength of CMF by 175%. In this paper, the deformation mechanism of CMF and LS-CMF were also discussed. [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]

The microstructure evolution and phase formation in novel Ti-(SiC f /Al 3 Ti) laminated composite were emphatically investigated via exploring the microstructures concerning different processing stages. The mechanical properties and fracture behavior of the composite were studied using compression, three-point bend (TPB) and single-edge notched beam (SENB) methods. The results indicated that the microstructure evolution of Ti-(SiC f /Al 3 Ti) laminated composite involved the solid-state and solid-liquid reaction of Ti and Al during hot pressing. In addition, Ti-(SiC f /Al 3 Ti) laminated composite generally possessed superior fracture toughness, compressive and bending strength than those of Ti-Al 3 Ti due to the addition of SiC fibers. The fiber breakage and interface debonding behavior was observed, confirming the expected toughening mechanisms associated with arrested and deflected behavior of the crack. Furthermore, when subjected to external bending and compressive stresses, the laminated composite displayed similar failure characteristic, containing the fragmenting of Al 3 Ti and cracking or buckling of Ti. Moreover, the main cracks oriented at 45° to layers in the bending and compressive specimens under perpendicular load. Nevertheless, the main crack carved all layers, propagating with a tortuous path in the edge-notched specimen along the loading direction. Additionally, the specimens were catastrophically fractured under compressive load and non-catastrophically fractured under bending load. [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]

An optimized continuous ceramic SiC and shape memory alloy NiTi hybrid fibers reinforced Ti-Al metal-intermetallic laminated composite (as-optimized CSMAFR-MIL) was designed and fabricated using vacuum hot pressing sintering technique. The microstructure characterization of the composite was performed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffractometer (XRD). The formation mechanisms of the intermetallic layer were discussed. Furthermore, the mechanical properties of the as-optimized CSMAFR-MIL composite were measured via tensile tests. The experimental results indicated that the NiTi fibers were exhausted, and the inhomogeneous intermetallic layer was formed containing Al 3 Ni, Al 3 Ti, Al 3 Ti 0.8 V 0.2 intermetallics due to the reactions of Al with NiTi and Ti-6Al-4V alloy. Meanwhile, the intermetallic centerline, which usually appeared in Ti-Al laminated composite, was significantly eliminated in the as-optimized CSMAFR-MIL composite due to the diffusion reaction between NiTi fiber and Al. In addition, the SiC fibers combined well with the intermetallics, and the interfacial phases TiC and Al 4 C 3 were formed around the SiC fiber. Moreover, compared to continuous SiC fiber reinforced Ti-Al metal-intermetallic laminated (CFR-MIL) composite, the as-optimized CSMAFR-MIL composite possessed a good combination of high strength and superior ductility owing to the optimized microstructure of the composite and the mixed fracture mode of intermetallics. [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 Ti6Al4V-Mg3AlZn laminate metal composite (TC4-AZ31 LMC) was successfully prepared by hot pressing sintering. The interfacial microstructure of this composite was investigated using scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD) and high resolution transmission electron microscopy (HR-TEM). The three-point bending (TPB) tests of TC4-AZ31 LMC were performed to determine the foil-foil interface bonding properties. Results show that the AZ31 matrix of the TC4-AZ31 LMC possesses a strong {10-10} <0001> sheet texture and the adjacent AZ31 foils are bonded well through the migration of grain boundaries across the original boundaries of the foils. A continuous interfacial reaction layer consisting of an intermetallics layer, a nanocrystalline-amorphous mixture layer and a bulk-precipitated particles region was formed around the TC4/AZ31 interface. The intermetallics layer bordering on TC4 reinforcement was identified as Al 192.40 Fe 46.22 phase. The nanocrystalline-amorphous mixture layer was composed of MgO nanocrystalline and Mg-O amorphous phase. The bulk-precipitated particles locating at the boundary of AZ31 matrix were determined as complex precipitates containing Al 6 Mn and Al 13 Fe 4 phases. Compared with the AZ31 alloy, the TC4-AZ31 LMC possessed a superior bending strength, which is attributed to the effective load transfer capability from the AZ31 matrix to high strength TC4 reinforcement through the well-bonded TC4/AZ31 interface. • The interfaces of TC4-AZ31 LMC were studied by EBSD and TEM systematically. • The extremely thin intermetallics and nanocrystalline-amorphous reaction layers were formed along the TC4/AZ31 interface. • The grains of AZ31/AZ31 interface were bonded together by grain boundaries migration. • The composite showed superior bending properties than AZ31 alloy. [ABSTRACT FROM AUTHOR]