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Laser brazing is an esteemed technique for Ti/Al dissimilar alloy welding, yet the emergence of brittle intermetallic compounds (IMCs) restricts its broader application. In-depth knowledge of IMCs formation provides critical insights for process optimization targeting IMCs structural improvement, pivotal to high-performance of Ti/Al joint. Herein, we establish macroscopic heat transfer-fluid flow coupled model for laser brazing welding of Ti/Al dissimilar alloys firstly, followed by a comprehensive characterization of the types, distribution, and crystallographic features of IMCs, thereby elucidating the impact mechanism of laser offset on IMCs growth. Incremented laser offset prompts a conversion from transverse to tangential flow at the Ti/Al interface, attenuates peak temperatures and liquid phase duration, and significantly revises solidification parameters, thereby reducing the IMCs layer to 5 μm, augmenting solid-state transformation characteristic, and diversifying crystallographic orientations of IMCs. Ultimately, enhanced tensile strength in the Ti/Al joint is attributed to the presence of thinner IMCs with finer grains, produced by larger laser offset. This article constitutes a pivotal progression in modeling heat transfer-flow behaviors for Ti/Al laser brazing welding, revealing IMCs genesis with unparalleled granularity guided by crystal selective growth principles. It also lays a theoretical foundation for IMCs micro-structure improvement strategy via temperature-flow regulation.

Graphene oxide (GO) membranes enabled by subnanosized diffusion channels are promising to separate small species in membrane distillation (MD). However, the challenge of effectively excluding small volatiles in MD persists due to the severe swelling and subsequent increase in GO interlamination spacing upon direct contact with the hot feed. To address this issue, we implemented a design in which a polymer is confined between the GO interlaminations, creating predominantly 2D nanochannels centered around 0.57 nm with an average membrane pore size of 0.30 nm. Compared to the virginal GO membrane, the polymer-intercalated GO membrane exhibits superior antiswelling performance, particularly at a high feed temperature of 60 °C. Remarkably, the modified membrane exhibited a high flux of approximately 52 L m–2h–1and rejection rates of about 100% for small ions and 98% for volatile phenol, with a temperature difference of 40 °C. Molecular dynamics simulations suggest that the sieving mechanisms for ions and volatiles are facilitated by the narrowed nanochannels within the polymer network situated between the 2D nanochannels of GO interlaminations. Concurrently, the unrestricted permeation of water molecules through the multinanochannel GO membrane encourages high-flux desalination of complex hypersaline wastewater.

Taking advantage of natural resources for freshwater production is the key to alleviating crises during maritime emergencies. Herein, we designed an asymmetrically superwettable Janus membrane for all-day freshwater harvesting; use of this membrane provided a high-quality freshwater supply with excellent solar desalination of 1.55 kg m−2h−1(daytime) and fog collection of 11.31 kg m−2h−1(nighttime).

The isothermal viscoelastic finite element method is used to simulate and analyze the process of cable coating extrusion, in which the Navier slip model is adopted. The Phan–Thien–Tanner differential viscoelastic constitutive equation is used to describe the flow characteristics of the polymer melt. The polymer material used for simulation is polypropylene. The extrudate swell, velocity field, pressure field and shear stress field are calculated by finite element method. The influences of the gas-assisted extrusion and traditional extrusion on wall slip of cable coating extrusion are compared. The results indicate that the extrudate swell ratio is the largest under the condition of the complete slip between core wire and melt during traditional extrusion process. The increase of core wire dragging velocity can lead to the increase of slip velocity, the decrease of pressure and the increase of shear stress of melt. Gas-assisted extrusion can eliminate the negative effects caused by the slip of core wire or the increase of core wire dragging velocity. Therefore, gas-assisted extrusion can reduce the energy consumption, improve the cable coating layer quality and increase the production efficiency during extrusion process.

The welding of dissimilar Ti/Al hybrid structures is recognized as a critical technology for the high-performance/lightweight fabrication of aerospace and high-speed transportation components. Laser brazing welding, a recognized method for Ti/Al joining, is challenged by the formation of brittle intermetallic compounds (IMCs), which significantly compromises joint mechanical. Herein, pulsed laser pretreatment (PLP) is employed to butt surface, effectuating a 40 % enhancement in tensile strength of Ti/Al dissimilar joint under laser brazing welding. The influence of PLP on evolution of IMCs is comprehensively understood by numerical simulation. PLP induces a turbulent flow at Ti/Al interface and enhances thermal diffusion on Ti side, resulting in alternating distribution and diverse crystallographic orientations of IMCs with an average thickness reduced to 2 μm. Thereupon, the fundamental relationship between IMCs structure and mechanical performance is illuminated by exploring joint fracture failure behavior. PLP promotes the stochastic distribution of Ti3Al, curbing the cracking of brittle phase and its interfaces within IMCs layer, diverting crack propagation paths and markedly reducing extension rates, thereby effectively enhancing tensile strength. This article heralds a considerable advance in understanding the formation and fracture of IMCs for Ti/Al system. It further furnishes novel and unique insights into the improvement strategies for mechanical properties of Ti/Al dissimilar joint, based on surface texture “Riveting” and IMCs structure “Pinning”.

The aim of this paper is to research the effects of stop hole on crack turning, residual fatigue life and crack tip stress field, in which the location, size and shape of stop hole are considered. The numerical model is established according to M-integral technology, and crack turning angle is determined by maximum hoop stress criterion. The calculation results show that stop hole location has a significant effect on crack turning angle and residual fatigue life, and it should be drilled with a reasonable distance in vertical and horizontal direction around crack tip to achieve a better residual fatigue life retardation effect. The larger the stop hole size is, the wider effect range of stop hole on crack turning and residual fatigue life will be. The effects of elliptical stop hole on crack turning angle and residual fatigue life retardation are greater than that of round hole when the distance in vertical direction increases. Crack tip stress distribution is changed by increasing σyand decreasing σx, and the most dramatical changes occur at the circumferential direction of 90° and 270°.