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• Basal texture adjustment was achieved by strain path variation in SDE process. • Deformation mechanism and texture evolution were revealed by coupled FEM-VPSC model. • Shear strain path weakened fiber texture in core and strengthened plane texture in side. • Texture effect on yield strength and asymmetry was assessed via modified hall-petch. An integrated calculated approach based on weakly coupled finite element (FEM)-viscoplastic self-consistent (VPSC) model was established to simulate the texture evolution during the variable strain path extrusion process of magnesium alloys. The spiral die extrusion (SDE) process with additional circumferential shear deformation was applied to investigate the effect of path control on texture adjustment and verify the accuracy of the model. The results indicated that the additional spiral shear resulting from the overall inclined flow path effectively reduced the intensity of the {0002}//ED fiber texture by suppressing basal slip activation in the core area, while the local shear deformation along the spiral equal channel strain path led to the formation of an inclined {0002}//ND plane texture on the side. Using the modified Hall–Petch relationship, the correlation between texture and yield strength was quantified. Specifically, the weakening of the texture effectively suppressed {10–12} tensile twinning, which compensated for the deficiency of compressive yield strength without significantly sacrificing tensile yield strength, and thus improved the tension-compression asymmetry. Furthermore, the strongly inclined {0002}//ND plane texture inhibited the widespread activation of basal slip during tensile yielding, thereby enhancing the yield strength. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, the stress-strain behavior of sintered Ti2AlNb alloy obtained at the temperatures of 980 °C and 1080 °C with a strain rate of 0.5 s−1was investigated using compression tests under furnace heating and current heating. When deformed at 980 °C, the B2 phase texture orientation all exhibited <001>//ND and <101>//ND during current-assisted hot compression (CAHC) and furnace hot compression (FHC). With the deformation temperature increased to 1080 °C, the texture <001>//ND gradually moved towards the <111> texture direction during CAHC. The results were ascribed to the different microstructure evolution that dynamic globularization and DRX by electric current. It indicated that the current promoted the spheroidization of the O phase which did not change the texture orientation. However, as the temperature increased to 1080 °C, the current promoted dynamic recrystallization which resulted in big changes in B2 phase texture orientation. The current promoted the spheroidization of lath by accelerating the phase transformation of O→B2. The current affected the dynamic recrystallization (DRX) mechanisms by promoting the transformation of low-angle grain boundaries (LAGBs) into high-angle grain boundaries (HAGBs) through continuous absorption of dislocations. The true stain-stress curves indicated the reduction of the deformation resistance and enhancement of the deformability of the Ti2AlNb alloy, which was closely related to the microstructure evolution.

Significant improvement of bending properties (approximately 64.7%) for WE43 magnesium alloy was realized by weakening the basal texture and raising the deformation temperature. The mechanisms for such improvement were investigated in detail by combining the experiment and finite element model. The results concluded that the coupling effects of weak basal texture and high deformation temperature was the key reason producing the above improvement of bending properties. Specially, the TD sample with weak basal texture was more conducive to activating basal slip than the RD sample, resulting in its higher strain hardenability and consequently more significant bending properties. Based on weak basal texture, raising the deformation temperature could further improve the bending properties. This improvement mechanism was attributed to the abundant activations of non-basal slip instead of basal slip, which could increase the independent slip systems and efficiently delay the development of the strong basal texture. Moreover, the occurrence of partial DRV and DRX relieved the stress concentrations by consuming the dislocations, further improving the bending properties. The activations of these deformation mechanisms matching the corresponding bending stress states caused the crystal rotation and the texture variety in the bending samples. Basal slip activation aligned the (0002) basal planes parallel to tensile stress in the outer region or perpendicular to compressive stress in the inner region. Additionally, prismatic slip activation induced crystal rotation around the c-axis, developing <10-10>//LD texture in the outer region but <10-10>⊥LD texture in the inner region.

A portable microwave atmospheric pressure cold air plasma jet based on a coaxial resonant structure was designed. To lower the plasma excitation power and get higher power efficiency, a tuning structure was added to overcome the manufacturing errors and to compensate for plasma impedance after excitation. The minimum self-excitation power of air by the device was 120 W, and its sustaining power was as low as 50 W. Experiments showed that by tuning the sliding short circuit, the power efficiency of up to 99% in a wide input power range and significantly longer plasma plumes were achieved.

A microwave-induced room-temperature atmospheric-pressure flexible microplasma source based on a resonant microstrip array structure was designed. This device was a simple structure with a small size, low power requirement, and flexibility. The utilization of a resonant microstrip was to reduce the excitation power requirement and plasma temperature. An array structure was adopted to achieve a larger plasma area. Experiments showed that it can induce an argon discharge at atmospheric pressure with as low as 20 W microwave input power. The temperature was around 30 °C. This device was designed to be suitable to manipulate different material treatments without being affected by the shape of the material itself.

To investigate the feasibility of spinning the welded aluminum alloys, hot spinning tests were conducted on the electron beam welded (EBWed) 2219 aluminum alloy thick plates at 400 °C and successfully obtained a 2.8 mm curved welded-spun plate with a total thickness reduction of 72 %. The abnormal grain growth (AGG) phenomenon of the base material during hot spinning could be observed due to the reduced pinning effect of the θ-Al2Cu phases and static recrystallization, while the fusion zone exhibited homogeneous recrystallized microstructure. After hot spinning, the yield strength of the base material increased from 89.3 MPa to 133.6 MPa and the yield strength of the joint increased from 93.1 MPa to 134.7 MPa. To further optimize the microstructure and improve the mechanical properties of the spun alloy, the subsequent solid solution and aging treatment were conducted. Most of the coarse θ particles dissolved into the matrix and a large quantity of needle-like θ′ precipitates were generated. The yield strengths of the base material and the joint increased to 213.1 MPa and 216.4 MPa, respectively, which was mainly attributed to the precipitation strengthening of the θ′ precipitates. The comparison between the calculated yield stress and the experimental results showed that the contributions of different strengthening mechanisms in strengths were reliable.

A series of hot plane strain compression (PSC) experiments of the extruded Mg-6.03Zn-0.55Zr alloy were conducted on the Gleeble-3500 machine with strain rates of 0.01 s−1to 10 s−1and temperatures ranging from 300 °C to 500 °C to reveal the microstructure evolution during the secondary process. The effects of grain refinement and texture modification which were easily affected by the deformation mechanism and dynamic recrystallization (DRX) were systematically studied. Experimental results showed that the main deformation mechanism during PSC was basal slip (74.3 %–94.9 %) and assisted by prismatic slip (4.8 %–21.1 %) and pyramidal slip (0.3 %–4.6 %). Since the pyramidal slip and prismatic slip were more preferred to activate owing to the significant decrease of critical resolved shear stress (CRSS) at a higher temperature, the activation of non-basal slip promoted the c-axes of the grains deviated from compression direction which weakened the basal fiber texture. Moreover, the activation of non-basal slip could promote DRX behavior to some extent. Further analysis of the DRX mechanism showed that the continuous DRX (CDRX) by continuous rotation of low angle grain boundaries was dominant at lower temperatures and higher strain rates, while discontinuous DRX (DDRX) which nucleated at the grain boundaries played a more and more important role as the temperature increased and strain rate decreased. After characterizing the orientations of the DRXed grains, the CDRXed grains owned a similar grain orientation with the deformed grain while the DDRXed grains exhibited a fairly dispersed distribution, indicating that the weakening effect of the basal texture was greater with a higher DDRX fraction.

In response to the problem that intense basal texture seriously affects the low-cycle fatigue life of magnesium alloys, the compression-extrusion process for basal texture weakening was implemented in ZK61 magnesium alloys. The low-cycle fatigue life under uniaxial symmetrical tension-compression cyclic loading was dramatically improved by basal texture weakening, up to 1.5∼3 times that in an intense-textured state. Basal texture weakening promoted basal slip to dominate the cyclic deformation, thus significantly reducing the cyclic tension-compression asymmetry caused by the {10–12} twinning-detwinning. Further, the suppression of {10–12} twinning and the decrease of compressive plastic strain slowed down dislocation accumulation inhibiting the cyclic hardening and fatigue crack initiation. The Manson-Coffin equation was feasible to predict the fatigue life of the intense-textured and weak-textured ZK61 magnesium alloys. The promotion of basal slip arising from basal texture weakening led to the decrease of fatigue ductility coefficient and the increase of fatigue ductility exponent contributing to the higher fatigue life.

Designing shape-controlled Pt-based core–shell nanocrystals is a prospective strategy to maximize the utilization of Pt while maintaining high activity for oxygen reduction reaction (ORR). However, the core–shell structures with ultrathin Pt shell exhibit limited electrochemical durability. Therefore, a thicker shell is proposed to successfully improve the durability of the core–shell structures by preventing the core from dissolution. Nevertheless, the deposition of Pt tends to switch to the Stranski–Krastanov (S–K) growth mode with the increase of the number of layer, resulting in the absence of a conformal morphology. Herein, we realize the deposition of three-to-five-layer epitaxial Pt–Co layers on Pd octahedral seeds by introducing tensile strain in the epitaxial layer to impede the S–K growth. The as-obtained Pd@Pt-Co octahedra with four layers exhibit enhanced mass activity (0.69 A/mgPt) and specific activity (1.00 mA/cm2) for ORR, which are 4.93 and 5 times that of the commercial Pt/C, respectively. Furthermore, it shows only 17% decay for specific activity after a 30,000-cycle durability test. This work is expected to enlighten the design and synthesis of related core–shell nanocrystals with facetted multicomponent shells, offering a promising strategy for designing cost-effective and efficient catalysts.

The Ti2AlNb alloy and TiBw/Ti64 composites were successfully bonded using a Ti interlayer at 900°C–1050°C for 20–80 min. The interface of the joints showed a layered microstructure. Moreover, the width of the diffusion zone gradually increased from 30 to 58 µm owing to sufficient atomic diffusion and phase transition at higher bonding temperatures with longer bonding times. The elemental concentration gradients caused by atomic diffusion promoted the precipitation of the O phase (Zone I) and the growth of the lamellar α phase (Zone II). A well-bonded joint was obtained and showed the highest shear strength of 460.9 MPa. Microcracks emerged in the diffusion zone and propagated into the TiBw/Ti64 substrate during the shear test, and the fracture mechanism inside the composites was intergranular ductile fracture mode.

The Ti2AlNb alloy and TiBw/Ti64 composites were successfully bonded using a Ti interlayer at 900°C–1050°C for 20–80?min. The interface of the joints showed a layered microstructure. Moreover, the width of the diffusion zone gradually increased from 30 to 58?µm owing to sufficient atomic diffusion and phase transition at higher bonding temperatures with longer bonding times. The elemental concentration gradients caused by atomic diffusion promoted the precipitation of the O phase (Zone I) and the growth of the lamellar a phase (Zone II). A well-bonded joint was obtained and showed the highest shear strength of 460.9?MPa. Microcracks emerged in the diffusion zone and propagated into the TiBw/Ti64 substrate during the shear test, and the fracture mechanism inside the composites was intergranular ductile fracture mode.

Hot shear-compression deformation (HSCD) of in situ TiBw/Ti6Al4V composites with network architecture was conducted at variant temperature from 1123 to 1223 K and strain rate from 10−3to 10−1s−1by using shear-compression specimens (SCS). According to equivalent stress and strain curves, the activation energy was calculated to be 631.1 kJ/mol in α+β phase region. In addition, the appearance of shear bands in the gage region was a typical evidence that shear was the major deformation during HSCD. Furthermore, dynamic recovery (DRV) and dynamic recrystallization (DRX) occurred in the shear bands, resulting in a decrease in flow stress. The mechanism of DRX in α+β phase region included the continuous rotation of substructure which was attributed to continuous dynamic recrystallization (cDRX) and formation of fine equiaxed grains which experienced nucleation and growth was attributed to discontinuous dynamic recrystallization (dDRX). Additionally, the existence of TiBw could promote the process of DRX by providing high density dislocations and nucleation sites.

AbstractThis article proposed a new solution to do the plasma cleaning under low pressure based on a domestic microwave oven. A conical bottle was placed in the oven according to the electric field distribution calculated by finite element method and Helmholtz equation. A vacuum pump was employed to make a low pressure environment in the bottle to generate plasma. Experiments demonstrated that discharges in the domestic microwave oven under low pressures from 100 Pa to 300 Pa can be easily triggered and maintained when the working gases were argon and air. The lower the pressure was, the easier to trigger and generate plasma, and the more uniform the plasma inside the conical bottle was. Experiments also found that this low-pressure Ar plasma generated in the domestic microwave oven can efficiently clean up the oils on the metallic sheets or glass substrates without damaging them.

TiBw/TA15 composite bars with in situ synthesized TiBw were successfully manufactured by the hot-pressing sintering and subsequent hot canned extrusion. Microstructure evolution and mechanical behavior of as-sintered and as-extruded composites had been systematically investigated. After extrusion, due to the large deformation degree, significant grain refinement occurred and the long axes of whiskers were almost parallel to the extrusion direction. Almost no micro-voids were caused by the fractured TiBw as a consequence of three-dimensional compressive stress during the extrusion process. The mechanical properties results demonstrated that the ultimate tensile strength, elongation and Vickers hardness of the as-extruded composites all increased compared with that of the as-sintered composites. Moreover, there was an inhomogeneous microstructure in the as-extruded composites. The edge part possessed stronger grain refinement and much weaker texture than that of the central part owing to the different deformation degree. The interface between the titanium matrix composites and the capsule (45# steel) was relatively flat with no interfacial reaction, which showed the superiority of the 45# steel as the capsule for hot canned extrusion. Oxygen content result illustrated that there was no significant oxidation of titanium matrix during the sintering and extrusion process.

High-entropy alloys (HEAs) have garnered considerable attention as promising nanocatalysts for effectively utilizing Pt in catalysis toward oxygen reduction reactions due to their unique properties. Nonetheless, there is a relative dearth of attention regarding the structural evolution of HEAs in response to electrochemical conditions. In this work, we propose a thermal reduction method to synthesize high entropy nanoparticles by leveraging the confinement effect and abundant nitrogen-anchored sites provided by pyrolyzed metal–organic frameworks (MOFs). Notably, the prepared catalysts exhibit enhanced activity accompanied by structural reconstruction during electrochemical activation, approaching 1 order of magnitude higher mass activity compared to Pt/C in oxygen reduction. Atomic-scale structural characterization reveals that abundant defects and single atoms are formed during the activation process, contributing to a significant boost in the catalytic performance for oxygen reduction reactions. This study provides deep insights into surface reconstruction engineering during electrochemical operations, with practical implications for fuel cell applications.

The rolling direction (RD) and the transverse direction (TD) samples were obtained from an as-rolled ZK60 magnesium alloy sheet with strong anisotropy of initial texture and their mechanical properties were tested at various deformation temperatures. Meanwhile, the microstructure and texture of these samples after fracture were investigated. Results revealed that a higher flow stress along the RD than that along the TD at room temperature were ascribed to the strong anisotropy of transitional texture, and this texture effect was remarkably weakened with the increase of deformation temperature. Deformation structure was dominant at 100 °C, and was replaced by dynamic recrystallization structure when the deformation temperature increased to 200 °C and 300 °C. The texture presented a strong texture (transitional texture in the RD sample and basal texture in the TD sample) at 100 °C, but its intensity visibly decreased and texture components became more disperse at 200 °C and 300 °C. These microstructure and texture results were employed in conjunction with calculated results to argue that raising deformation temperature could increase the activity of non-basal slip by tailoring the relative critical resolved shear stress of each deformation mode and finally result in low texture effect on mechanical anisotropy. [ABSTRACT FROM AUTHOR]

The effect of plastic deformation on the properties and microstructure of W–Cu composites produced by multi-pass hot extrusion with steel cup was investigated. W–Cu composites were sintered at 1 100 °C and then the sintered billets were firstly extruded at 900 °C with different extrusion ratios. The second hot extrusion was performed at 900 °C. The plastic deformation of copper phase plays a dominant part during the whole extrusion process. The microstructural evolution of W phase during the whole processing of heavy hot deformation can be divided into different stages. Experimental results indicate that the W agglomeration will be broken into fine particles effectively when the accumulated plastic deformation amounts to 97.6 % after the second extrusion.

Continuous-flow microwave reactors find widespread application in chemical production. However, dynamic changes in the dielectric constant of reactants result in a low microwave energy efficiency. This paper reveals a circular waveguide developed using a meta-surface unidirectional propagation of microwaves. This waveguide was integrated into a continuous-flow heating system that efficiently heats materials with varying dielectric constants. A multiphysics model incorporating electromagnetic, fluid heat transfer, and chemical engineering has been built to analyze the microwave heating performance under different loads. Based on simulation and experimental findings, the meta-surface can achieve an energy efficiency of over 90% for loads with dielectric constants from 10 to 80. Moreover, a continuous-flow heating experiment conducted for biodiesel production indicated that meta-surfaces can enhance the heating efficiency by over a quarter. This research presents a promising approach toward efficient continuous-flow microwave heating, which can potentially revolutionize large-scale chemical production in industry.

Fine-grained, high-strength and high-ductility Mg-2.5Nd-0.5Zn-0.5Zr alloy sheets were prepared by multi-pass hot rolling with ultimate tensile strength of 311.9 MPa, yield strength of 272.4 MPa, elongation of 17.1%, and the average grain size of 4.25 μm. After multi-pass hot rolling, all plates showed the characteristics of bimodal rolling direction-tilt texture (with the basal poles tilting at about ±15–20° form normal direction towards rolling direction). With the increase of rolling passes, the basal texture strength decreased gradually, which was 9.5 (1st pass), 7.5 (2nd pass) and 5.4 (3rd pass), respectively. The ductility improvement was the result of the interaction of texture weakening, basal slip and non-basal slip actuation.

Magnetic microbubbles (MMBs) are microbubbles (MBs) coated with magnetic nanoparticles (NPs). MMBs not only maintain the acoustic properties of MBs, but also serve as an important contrast agent for magnetic resonance imaging. Such dual-modality functionality makes MMBs particularly useful for a wide range of biomedical applications, such as localized drug/gene delivery. This article reports the ability of MMBs to release their particle cargo on demand under stable oscillation. When stimulated by ultrasound at resonant frequencies, MMBs of 450 nm to 200 μm oscillate in volume and surface modes. Above an oscillation threshold, NPs are released from the MMB shell and can travel hundreds of micrometers from the surface of the bubble. The migration of NPs from MMBs can be described with a force balance model. With this technology, we deliver doxorubicin-containing poly(lactic-co-glycolic acid) particles across a physiological barrier both in vitro and in vivo, with a 18-fold and 5-fold increase in NP delivery to the heart tissue of zebrafish and tumor tissue of mouse, respectively. The penetration of released NPs in tissues is also improved. The ability to remotely control the release of NPs from MMBs suggests opportunities for targeted drug delivery through/into tissues that are not easily diffused through or penetrated.