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The aging and damage of artificial skin materials for artificial intelligence robots are technical problems that need to be solved urgently in their application. In this work, poly (vinylidene fluoride) (PVDF) fibers containing a liquid agent were fabricated directly as biomimetic microvasculars, which were mixed in a glycol–polyvinyl alcohol–gelatin network gel to form biomimetic self-healing artificial skin composites. The self-healing agent was a uniform-viscous buffer solution composed of phosphoric acid, acetic acid, and sodium carboxymethyl cellulose (CMC-Na), which was mixed under 40 °C. Microstructure analysis showed that the fiber surface was smooth and the diameter was uniform. SEM images of the fiber cross-sections showed that there were uniformly distributed voids. With the extension of time, there was no phenomenon of interface separation after the liquid agent diffused into the matrix through the fiber cavity. The entire process of self-healing was observed and determined including fiber breakage and the agent diffusion steps. XRD and FT–IR results indicated that the self-healing agent could enter the matrix material through fiber damage or release and it chemically reacted with the matrix material, thereby changing the chemical structure of the damaged matrix. Self-healing behavior analysis of the artificial skin indicated that its self-healing efficiency increased to an impressive 97.0% with the increase in temperature to 45 °C. [ABSTRACT FROM AUTHOR]

Sc microalloying and isothermal multidirectional compression (IMC) are important methods to refine grains and improve the mechanical properties of Al–Zn–Mg–Cu–Zr alloys. Herein, EBSD, SAXS and TEM have been carried out to investigate the effect of IMC and minor Sc on the microstructure, especially for grain boundary wetting, and mechanical properties of aged Al–Zn–Mg–Cu–Zr alloys by melting and hot compression process parameter optimization. The results show that the strength and plasticity can be obviously improved simultaneously by minor Sc addition and IMC. Especially, stripy GBs (one kind of typical GB complexion) have been widely observed for alloy samples after microalloying Sc and IMC, which indicates the occurrence of GB wetting for Al–Zn–Mg–Cu–Zr alloy. And the GB wetting degree gradually increases for alloys with only microalloying Sc, only IMC and (microalloying Sc + IMC). Combined with GB wetting, the formation of Al 3 (Sc, Zr) due to Sc addition could inhibit the motion of dislocation and grain boundary, which promotes formation and inhibit growth of recrystallized grains, leading to further grain refinement. Besides, GB wetting degree would affect the precipitate distribution, especially for grain boundary precipitates. Also, GB wetting probably promote grain bridging, which is beneficial to improve the yield strength and ductility of Al–Zn–Mg–Cu–Zr alloys. The concurrent effect of grain refinement, the precipitate including finer Al 3 (Sc, Zr) particles, dislocation strengthening and grain bridging contribute to the simultaneous improvement of the strength and ductility of Al–Zn–Mg–Cu–Zr alloys under IMC and Sc. This study provides a new understanding on microalloying Sc combined with IMC on the microstructure and properties of Al–Zn–Mg–Cu–Zr alloys. [Display omitted] • IMC and minor Sc induce nonlinear GB wetting of Al–Zn–Mg–Cu–Zr alloy. • Sc, IMC and (Sc + IMC) cause gradually increased GB wetting degrees. • Minor Sc promotes formation and inhibits growth of recrystallization grain. • GB complexion transition affecting the mechanical properties of alloys. [ABSTRACT FROM AUTHOR]

• "Si-O-Si" could refine the pore structure together with hydration products to improve the anti-efflorescence of the coating. • KH-560 could improve the compatibility between PA and PDMS, reducing the deterioration of mechanical properties by PDMS. • The efflorescence area of the modified-coating containing MP and 0.3 wt% SA was only 1.58%. The objective of this paper was to prepare a novel type of anti-efflorescence cement-based coating with excellent mechanical properties using the modified polyacrylate emulsion (MP) and silicon-aluminum based powder (SA), and provided an optimum proportion. Silica sol (SS) and polydimethylsiloxane (PDMS) were selected as modified components to incorporate into polyacrylate emulsion (PA). The synergistic effect of MP and SA on the tensile strength, water absorption, hydration process, microstructure and anti-efflorescence property of cement-based coatings were investigated. The research results demonstrated that the tensile strength and waterproof in coating containing MP and 0.3 wt% SA were increased by about 73.4% and 52.1%, respectively, compared with the reference sample. The reason could be attributed to the densification of the internal structure due to the formation of "Si-O-Si" structure and pozzolanic effect of SA. In addition, the hydrophobic PDMS can hinder the migration of water and salt, thereby limiting the diffusion of alkali ions outward. Hence, the efflorescence area of the modified-coating was decreased to 1.58%. [ABSTRACT FROM AUTHOR]

Recently, an efficient integrated forging process has been proposed in which solutionized aluminum alloy extruded bars are directly hot forged and quenched. In this study, the hot deformation behaviors and microstructure evolution of 6082 aluminum alloy extruded bar was investigated via isothermal compression tests under the temperature range of 400–535 ℃ and strain rates range of 0.1–10 s−1 with different strains. The deformation behaviors were described by the established strain-compensated constitutive model and processing maps. The microstructure evolution of the deformed specimens was revealed by electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM). It was found that the Zener-Hollomon (Z) parameter, which involved temperature and strain rate, exerted a considerable influence on the deformation behaviors and microstructure evolution. Deformation-induced extensive dislocations were pinned by the dispersoids and generated cellular substructures under high ln Z (i.e. low temperature or high strain rate), potentially triggering dynamic instability. The tangled dislocations pinned by the insoluble dispersoids continued to overcome the pinning points as ln Z decreased, while the dislocations were consumed by the rotation of subgrain boundaries. As a result, the geometrically necessary dislocation (GND) was decreased with the significant increase of the fraction of high angle grain boundaries (HAGBs). In addition, the stable-end orientations, namely, Brass {011}< 211 > and Goss {011}< 001 > texture components with high Schmid Factors (SFs) are generated during compression, facilitating the dislocation movement and thus promoting the fraction of recrystallization. The above findings demonstrate the foundation for improving forming performance and optimizing the processing parameters for the integrated forging process. • The flow behaviors of solutionzied 6082 aluminum alloy extruded bars were investigated. • The relationship of the dominant softening mechanisms and the Z parameter was revealed. • Evolution of grain boundaries misorientation and geometrically necessary dislocation was illustrated. • The characteristics of grain orientation and Schmid Factors were investigated. [ABSTRACT FROM AUTHOR]

In this work, the microstructural evolution and mechanical properties of aviation M50 steel under a novel quenching-electroshocking-tempering (Q-E-T) process were investigated. Microstructural observations indicate that the carbon concentration and volume fraction of retained austenite (RA) in Q-E-T specimens are higher than those in conventional quenching‐tempering (Q‐T) specimens due to the significant carbon partition induced by the introduced electroshocking treatment (EST). Meanwhile, the diameter of packets in the Q-E-T specimens is refined from 1.71 μm to 1.34 μm, which is attributed to the segmentation of blocky as-quenched RA by bainite transformation during EST. The mechanical analysis shows that an excellent combination of ultimate tensile strength and impact toughness is achieved for M50 steel subjected to the Q-E-T process. Compared with the conventional Q-T process, the impact absorbing energy of M50 steel is increased by 24.1% without any loss of tensile strength. Additionally, the thermal and mechanical stabilities of RA in the Q-E-T specimens are both improved. This work provides a novel strategy for improving the impact toughness of M50 by refining the microstructure and appropriately tailoring the stability of RA via an efficient Q-E-T process. [ABSTRACT FROM AUTHOR]

[Display omitted] • An excellent metallurgic bonding was achieved for NiTi/Cu with increased laser pulse duration. • Segregation like peninsula and beaches was in fusion zone for 5 and 8 ms, but it was absent for 15 ms. • Liquidus temperature in molten pool was the key for segregation due to increased pulse durations. • The fraction of Ni-Ti brittle IMCs in the fusion zone decreased, replaced by Cu-Ti IMCs. • It is potential to improve mechanical property of NiTi/Cu joint by adjusting laser pulse duration. In this study, laser microwelding was adopted to join NiTi and Cu wires using different laser pulse duration. The cross section of welded samples showed no visible defect, but some intermetallic compounds were formed inside the fusion zone. An excellent metallurgic bonding was achieved during laser welding for NiTi and Cu wires with increasing pulse duration. Local element segregation like peninsulas and beaches was observed in the fusion zone for the pulse duration of 5 and 8 ms, but the segregation was absent with the pulse duration increased to 15 ms. The liquidus temperatures of weld metals in molten pool had a significant effect on the segregation formation. If T LW < T LNiTi /T LCu , a NiTi/Cu peninsula can form near the fusion boundary of NiTi/Cu side, while a NiTi/Cu beach can form if T LW > T LNiTi /T LCu. With increasing pulse duration, the fraction of Ni-Ti brittle intermetallic compounds in the fusion zone decreased, but Cu-Ti intermetallic compounds with lower hardness increased. Little hardness variation was achieved and peak hardness values decreased (~630 → ~560 → ~490 HV). The joint with the pulse duration of 5 ms displayed poor mechanical properties due to uncompleted penetration. Fracture occurred in Cu base metal for the pulse duration of 8 ms and 15 ms. This study showed that it was potential to diminish the brittle intermetallic compounds and improve the mechanical properties of fusion zone by adjusting the laser pulse duration for the dissimilar laser welding of NiTi and Cu wires. [ABSTRACT FROM AUTHOR]

A novel electromagnetic shocking treatment (EST) has been put forward to optimize interface microstructure and further enhance the mechanical properties of titanium alloys. In details, tensile properties and impact toughness of TC11 titanium alloy have been investigated with room temperature tensile test and Charpy impact testing. Then, tensile fracture and impact fracture as well as microstructure including phase and interface are characterized and analyzed. The results show that after EST, the tensile strength increase slightly, the elongation decreases while the impact energy is enhanced obviously. Besides, with the maximum temperature rising on alloy sample surface being limited to just 210 °C, EST promotes the phase transformation from β to α instantly, also, wrinkling at interface is more commonly observed in EST sample, which indicates that nonlinear interface wetting and bridging are promoted by EST. It demonstrates that the increase of α mainly accounts for the slight improvement of tensile strength and the decrease of elongation. Also, considering that the phase transformation from β to α is unfavorable to the improvement of impact toughness, the degree of interface wetting and bridging which is dependent on the electromagnetic shocking energy plays a decisive role for the enhancement of impact energy of EST sample. This work provides a novel EST method to selectively embellish interface and further to improve the properties and performance of solid alloys related with interface microstructure. • EST enhances impact toughness of TC11 titanium alloy by embellishing interface. • EST induces nonlinear interface wetting and further promotes interface bridging. • EST promotes β.→α solid phase transformation instantly by interface wetting. [ABSTRACT FROM AUTHOR]

[Display omitted] • The thickness of Al 2 O 3 oxide film (18.45 nm) on the surface of the aluminum substrate is determined by XPS depth profiling. • After surface modification (tin plating), the contact angle between the tin solder joint and the aluminum substrate is significantly decreased (110°→14°). • The Cu-based component/aluminum laser soldering joint without defects is obtained, and the maximum linear load increases from 0 to 95.2 N/mm after tin plating. Cu-based component/aluminum substrate solder joint is achieved through laser soldering technology in this paper. The solder wettability on aluminum substrate and microstructure-properties of Cu-based component/aluminum substrate laser soldering joint are studied. The results show that the presence of the high melting point Al 2 O 3 oxide film (∼18.45 nm thickness) isolates the contact between the molten Sn-based solder and the aluminum substrate, which results in the poor wetting properties of aluminum substrate. The surface modification of aluminum substrate can significantly improve wettability (110°→14°). Anisotropic Sn dendrites appear in the brazing area of laser soldering joints, and Ag 3 Sn is precipitated in the β-Sn matrix. The (Cu, Ni) 6 Sn 5 IMC is formed near the Ni layer side. Due to the extremely fast cooling rate, the IMC thickness is less than 5 μm, and a continuous (Cu, Ni) 6 Sn 5 region with a thickness of less than 1 μm appears at the interface near the Ni layer side. The average maximum linear load of the laser soldering joints is 95.2 N/mm. The laser soldering joint fracture occurs along the brittle (Cu, Ni) 6 Sn 5 IMC formed at the Ni layer interface, and the fracture mode is mainly ductile fracture. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mixed solution of HF and HCl can effectively expand the pores and cracks inside the coal. • The effect of acidification of coal will change with temperature. • The best acidification temperature for this experiment is 50 °C. • The acid-heat coupling affects the element composition on the coal surface and the internal pore structure of the coal. To study the effect of acid-heat coupled fracturing on the damage of coal pores and fractures, scanning electron microscope-energy dispersive spectrometry (SEM-EDS), mercury intrusion porosimetry (MIP) were used to analyze. The results of the study show that the acid-heat coupling effect not only changes the microscopic morphology and element composition of the coal sample, but also promotes the formation of a pore-fracture network within the coal, and the connectivity is significantly increased, which is conducive to the diffusion and migration of coalbed methane. The optimum acidification temperature for the experiment is 50 °C. SEM observed that the acid-heat coupling changed the local stress sensitivity of the coal body and weakens the strength of the coal body to form a fracture network. EDS analysis shows that the element distribution on the coal surface changes regularly with the increase of acidification temperature, and the reduction rate of mineral content on the coal surface is highest at 50 °C. MIP and fitting analysis show that the pore parameters of coal samples will increase with the increase of acid-heat coupling temperature, reaching a peak at 50 °C, and the acidification effect will be relatively slow after increasing the temperature. This research is of great significance for exploring the optimal acidification conditions of coal mines, reducing acidizing fracturing costs, and ensuring coal mine safety production. [ABSTRACT FROM AUTHOR]

As an emerging technology to solve the bottleneck of plastic processing of light alloys, electromagnetic forming usually causes a complex mechanical response and microstructure evolution of materials. In this work, based on the electromagnetic ring expansion (EMRE) experiment, the relationship between microstructure evolution and mechanical properties of AA2219-T6 under EMRE with different discharge energies is established. In particular, to reveal the influence of strain and temperature parameters on the output response during the electromagnetic pulse process, a Q235 steel sleeve and an epoxy resin sleeve with different thermal conductivities are applied to constrain the deformation of the ring, respectively, thus the performance under electromagnetic treatment (EMT) are investigated. It is found that, under the threshold discharge energy of 4.23 kJ, the microhardness of the ring via EMT with the steel sleeve is similar to that of AA2219-T6, but increases by 20.9% compared with the ring via EMT with the epoxy sleeve and 17.1% compared with the ring via EMRE. The electromagnetic pulse has no significant effect on the evolution of precipitates in AA2219-T6-EMT (Steel), but the adiabatic temperature rise in AA2219-T6-EMT (Epoxy) caused redissolution of G.P.Ⅱ zones. With the gradual increase of discharge energy under EMRE, the microhardness of AA2219-T6 increases initially and followed by a decrease, while the fracture strain increases continuously. When discharge energy reaches 8.63 kJ, 2219 aluminum alloy has the optimal mechanical properties that, compared with AA2219-T6, the microhardness increased by 14.2% and the fracture strain increased by 18.0%. The dislocation density shows a trend of first increasing and then decreasing with the increase of discharge energy. Combined with the observed phase transformation, it is shown that dislocations generated by EMRE will promote G.P.Ⅱ zones to transform into θ ′′ phases, and affected by dislocation density, the transformation effect is most obvious at 8.63 kJ. In addition, the transformation of precipitates greatly increases the probability of hindering the motion of dislocations, which promotes the precipitates to be dispersed, and AA2219-T6 is further strengthened after EMRE. As discharge energy continues to increase, the dislocations begin to annihilate and G.P.Ⅱ zones are redissolved due to the adiabatic temperature rise. • G.P.Ⅱ zones are redissolved with a significant temperature rise in EMRE and EMT. • EMRE promotes the instant phase transformation affected by dislocation density. • The optimal performance under EMRE is obtained at a discharge energy of 8.63 kJ. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel electroshock treatment (EST) has been proposed to improve fatigue life of titanium alloy. • After appropriate EST, the transformed β phase was broken and more finely dispersed acicular secondary α phase was formed. • Appropriate EST led to dissolution of unstable phase AlTiHx and generation of nanoscale strengthening phase Al 24 Ti 8 at relatively low temperature. To improve the service life of titanium alloys, a novel electroshock treatment (EST) with low frequency, alternating pulse, and limited energy density is proposed in this study. The effects of different parameters process on the fatigue life of TC11 alloy were investigated. Experimental data show that low-cycle fatigue life of the alloys increased 22.5% by the appropriate EST. The mechanism affecting the fatigue life was studied by SEM and TEM. The results show that after the appropriate EST, the volume fraction of the α phase increased, the lath-like transformed β phase was broken and dissolved locally, accompanied by the formation of a secondary α phase and its morphological transformation from flake-like to more finely dispersed acicular. It was found that the appropriate EST led to the nanoscale solid-state phase transition; namely, the dissolution of an unstable brittle AlTiH x phase in the alloy matrix and precipitation of the Al 24 Ti 8 strengthening phase with a size close to 5 nm in the β phase. These transitions occurred when the local maximum temperature of the sample recorded was only 296.8 °C. In summary, the microstructural evolution and nanoscale phase transformation of titanium alloy by the EST process significantly increased the fatigue life. [ABSTRACT FROM AUTHOR]