B-site modified Bi3.25La0.75Ti3-xTaxO12 ceramics were prepared by the conventional solid-state reaction method. The influence of Ta2O5 on microstructure and electric properties of the ceramics was investigated. The results demonstrated that Ta5+ ions were dissolved into the perovskite lattice and homogeneously distributed in the matrix without forming any minority phase. The conduction mechanism and dielectric response behavior were transformed with Ta substation, which is triggered by varied structural distortion characteristics and defect diploes. The Curie temperature decreased gradually with increasing Ta content and a relaxor-like behavior was observed for x = 0.09 sample. The internal bias field is decreased with Ta doping, because the substitution of Ta5+ at B-site contributes to release the involved oxygen vacancies in defect diploes. Moreover, further increasing Ta content causes a reduction in the oxygen vacancies located at lattice misfits, resulting in a decrease of coercive fields. An improved ferroelectric properties were obtained for x = 0.09 sample with a relatively lower coercive field and a larger spontaneous polarization.

•Annealing time effects microstructures and tensile properties of the composites.•After 36 h diffusion bonding, Ni3Ti/TiNi laminated composite was fabricated.•The composite after 12 h annealing shows the best tensile properties.•TiNi layers influence tensile properties of the composites.The effects of annealing time on the microstructures and tensile properties of formed laminated composites in Ti-Ni system were investigated. The results showed that Ti2Ni, TiNi and Ni3Ti intermetallics were formed between the Ti and Ni foils after 1 h annealing. These intermetallics grew thicker with the increase of annealing time until the complete consumption of Ti layers. TiNi with two different crystal structures (B2 and B19′) were identified in the composites after 1 h and 6 h annealing. In the composites after 12 h, 18 h, 24 h and 36 h annealing, Ni4Ti3 phase in different shapes precipitated in different regions (interfaces and the interior) of TiNi layers, resulting in the multi-step martensite transformation behavior of TiNi layers. The tensile test results revealed that high TiNi content in the composite after 12 h annealing had the highest yield strength (391 MPa), ultimate tensile strength (912 MPa) and elongation (6.3%) of all the composites. With the increase of annealing time, the thickness of TiNi layers decreased and that of Ni3Ti layers increased, leading to the decrease of strength and elongation of the composites after18, 24 h and 36 h annealing, which indicated that TiNi layers had great influence on the strength and ductility of these composites.

The present work systematically investigated the influence of increasing Al concentration on the phase composition, microstructure evolution and mechanical behaviors of Ni1.5CoFeCu1−xAlxV0.5 (x = 0.1, 0.2, 0.3 mol) high entropy alloys (HEAs) synthesized by mechanical alloying (MA) followed by spark plasma sintering (SPS). In the MA powders, FCC phase reduced while BCC phase increased with increase in Al content. In the alloys consolidated by SPS, BCC phase disappeared with the formation of vanadium carbides as well as aluminum oxide due to carbon and oxygen contaminations. Microstructure characterization suggests that three bulk HEAs all displayed the bimodal grain microstructure, consisting of coarse-grained (CG) regions as well as fine-grained (FG) regions with uniform dispersion of aluminum oxide nanoparticles. Furthermore, with the increase of Al concentration in the alloy, the volume fraction of FG region increased gradually and the average grain sizes of CG and FG regions reduced dramatically. Since the microstructure refinement resulted in the enhancement of grain boundary strengthening, the yield strength of alloy was improved significantly with increasing Al. In addition, the increase of Al concentration remarkably changed the strain-hardening behavior of bulk HEA by influencing the strain-hardening stages during compression.

Ti2Ni/TiNi laminated composites with different TiNi volume fractions were fabricated by adjusting the thickness of initial Ti foils. The microstructure evolution was discussed. The compression properties and fracture toughness in different directions were systematically investigated. The results show that the formation of Ti2Ni/TiNi laminated composites experiences a complex diffusion process between Ti and Ni atoms. TiNi layers in the composites possess a complex monoclinic B19′-type crystal structure and Ti2Ni participates in the TiNi layers have a great effect on the ductility of the TiNi layers. The compression tests demonstrate that the compression strength and strain increase with the increase of the thickness of TiNi layers in both tested directions. The tests also reveal that whether the double yielding phenomenon can be obviously observed in compression curves is determined not only by martensitic re-orientation of TiNi layers, but also by the load distribution on different layers. The fracture toughness of the composites increases with increase of the thickness of TiNi layers in both orientations: in the divider orientation, it is related to the strength and ductility of TiNi layers; and in the arrester orientation, it is improved primarily through the mechanisms of crack bridging and deflection by TiNi layers.

•NixCoCuFeCr2−x (x = 1.0, 1.2, 1.5, 1.8 mol) HEAs are synthesized by MA and SPS.•Ni/Cr ratio evidently affects phase proportion in the MA powders and SPS-ed alloys.•Relatively homogeneous microstructure is observed in alloys with Ni/Cr ≥ 1.5/0.5.•The increase of Ni/Cr ratio has combination effect on mechanical properties.•Ni1.5CoCuFeCr0.5 alloy exhibit the best matching of strength and plasticity.NixCoCuFeCr2−x (x = 1.0, 1.2, 1.5, 1.8 mol) high entropy alloys (HEAs) were prepared by mechanical alloying (MA) and spark plasma sintering (SPS). The effect of the increase of Ni/Cr ratio in NiCoCuFeCr alloy system on the phase, microstructure, and mechanical properties was investigated. Results show that with increase in Ni/Cr ratio, FCC phase increased while BCC phase reduced in the MA powders, and after SPS Cu segregation gradually disappeared and σ phase transformed from BCC phase evidently decreased. When Ni/Cr ratio ≥1.5/0.5, relatively homogeneous microstructure was observed in the consolidated alloys. However, mechanical properties of the bulk HEAs did not change monotonously with the increase of Ni/Cr ratio. Among the four studied alloys, Ni1.5CoCuFeCr0.5 alloy, which had yield strength of 1009 MPa, compressive strength of 1985 MPa and plasticity of up to 29.5%, exhibited the optimal comprehensive mechanical properties.

In the present investigation, the dynamic compression properties and the sensitivity of the formation of adiabatic shear band in the Ti–6Al–4V alloyshaving equiaxed and bimodalmicrostructures were studied. The stop-ring technology traditionally used on the hat-shaped specimen was introduced to the compression experiments to control the engineering strain of the cylindrical specimen. The loading time (ti), the critical strain (εi) and the localization energy (Uloc) at which adiabatic shear band initiates were differentiated. The loading time (ti), the critical strain (εi) and the localization energy (Uloc) analyzed were found to be useful points in decoupling the homogenous plastic deformation and the adiabatic shear banding behavior in the dynamic deformation and fracture behavior of the investigated Ti–6Al–4V alloys. The loading time (ti), the critical strain (εi) and the localization energy (Uloc) were also chosen to quantitatively evaluate the sensitivity of the formation of adiabatic shear band in Ti–6Al–4V alloys having bimodal microstructures with identical primary equiaxed α and similar volume fraction of the transformed β matrix. The bimodal microstructure BA with the thickest α lamellar in the transformed β matrix demonstrated the lowest possibility of the formation of adiabatic shear band.

AlNbO4, as lithium-ion batteries (LIBs) anode, has a high theoretical capacity of 291.5 mAh·g−1. Here, AlNbO4 anode materials were synthesized through a simple solid-state method. The structure, morphology and electrochemical performances of AlNbO4 anode were systematically investigated. The results show that AlNbO4 is monoclinic with C2/m space group. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations reveal the AlNbO4 particles with the size of 100 nm–2 μm. As a lithium-ion batteries anode, AlNbO4 delivers a high reversible capacity and good rate capability. The discharge capacity is as high as 151.0 mAh·g−1 after 50 charge and discharge cycles at 0.1C corresponding to capacity retention of 90.7 %. When the current density increases to 5.0C, AlNbO4 anode displays reversible discharge capacity of 73.6 mAh·g−1 at the 50th cycle.

AbstractA novel ultra-high-strength bainitic steel was designed. The analysis of its mechanical properties by quasistatic testing showed that upper bainitic steel exhibited an ultimate tensile strength of 2260 MPa (engineering stress) and an ultimate compressive strength of more than 2700 MPa (true stress). The ultra-high strength of upper bainitic steel was mainly attributed to untempered martensite and upper bainite with a feather-like microstructure. Moreover, lower bainitic steel demonstrated an ultimate tensile strength of 1922 MPa (engineering stress) and an ultimate compressive strength of 2500 MPa (true stress). The ultra-high strength of lower bainitic steel was primarily due to untempered martensite and lower bainite with an acicular microstructure. The untempered martensite in the two kinds of bainitic steels was produced in different ways. The dynamic test results showed that the ultimate compressive strengths of the two bainitic steels were maintained at 1600 MPa (true stress) under high strain rates (1100 and 2200 s−1) at 600 °C, because of the added tungsten, confirming the satisfactory hot hardness property of the steel. Furthermore, lower bainitic steel showed better comprehensive mechanical properties than upper bainitic steel.

•Nanocrystalline Sm2Zr2O7 with the faceted morphology are successfully synthesized by a simple hydrothermal approach and an optimum hydrothermal process is proposed.•The structural stability of Sm2Zr2O7 nanoparticles depend on the crystallite size.•Pyrochlore Sm2Zr2O7 nanoparticles exhibit excellent photocatalytic activity.Pyrochlore Sm2Zr2O7 nanoparticles were synthesized by a facile hydrothermal method and their photocatalytic properties were investigated. The effects of hydrothermal temperature, reaction time and pH value on structures and morphologies of the resultant products were investigated. An optimum hydrothermal process was proposed based on these experiments. Pyrochlore Sm2Zr2O7 nanoparticles with an average size smaller than 18 nm were successfully prepared. The results showed that the structural stability of Sm2Zr2O7 nanoparticles was related to their crystal sizes. The nanoparticles with the sizes larger than 10 nm are found in the pyrochlore structure, while the smaller-size nanoparticles crystallize in the fluorite structure. The absorption spectrum of the Sm2Zr2O7 nanoparticles with the average size of 15 nm evidenced the existence of an absorption edge in the visible-light range. The photodegradation of the Congo red organic dye revealed that Sm2Zr2O7 nanoparticles exhibit excellent photocatalytic activity.

Effect of stress state including dynamic shearing and uniaxial dynamic compression on adiabatic shear banding (ASBing) of hot-rolling Ti–6Al–4V (TC4) alloy was investigated. The absorbed energy of specimen before failure was calculated to evaluate the susceptibility to adiabatic shear band (ASB) of TC4 alloy quantitatively. Results show that the susceptibility to ASB of hot-rolling TC4 alloy exhibits obvious anisotropy under both dynamic shearing and uniaxial dynamic compression conditions, but the anisotropy of susceptibility to ASB under dynamic shearing condition exhibits an opposite tendency with that under uniaxial dynamic compression condition. Under the condition of uniaxial dynamic compression, material shows the highest susceptibility to ASB when loaded along transverse direction (TD) of the hot-rolling TC4, while the lowest susceptibility when loaded along rolling direction (RD). However, under the condition of dynamic shearing, the material behaves in the opposite way, demonstrating the lowest susceptibility when loaded along TD of the hot-rolling TC4, while the highest susceptibility when loaded along RD.

Effect of microstructures on ballistic impact properties of Ti–6Al–4V targets was investigated. The 20 mm Ti–6Al–4V targets having different microstructures were impacted normally by the 12.7 mm AP. The RHA steel was used as the back target, and the residual depth of penetration in the RHA steel target was measured to evaluate the ballistic performance of the Ti–6Al–4V targets. Experimental results show that the bimodal microstructure with thicker α platelets in the transformed β matrix exhibited better ballistic impact property than the other microstructures. The failure modes of Ti–6Al–4V targets varied with the microstructures. In the equiaxed microstructure and the bimodal microstructures, ductile hole formation was the failure mode; while in the lamellar microstructures, the Ti–6Al–4V targets failed by the type of brittle fragmentation. Post-ballistic metallurgical observations reveal that the propagating features of adiabatic shear bands determined failure modes of Ti–6Al–4V targets having different microstructures. The brittle fragmentation failure mode in the lamellar microstructures was facilitated by net-like propagating features of adiabatic shear bands, while the ductile hole formation failure mode in equiaxed and bimodal microstructures was facilitated by the somewhat regularly spaced propagating features of adiabatic shear bands.