The quality of high-pressure die casting (HPDC) is largely determined by the process parameters. The objective is to study the influence of process parameters on melt filling and feeding capacity. The research is carried out by means of numerical simulations and orthogonal experiments. The results show that the influence of process parameters is different. The piston velocity of the fast stage has the most obvious impact. As the piston velocity of the fast stage increases, the filling capacity and feeding capacity also increase. The melt injection temperature should not be too low; otherwise, it would be easy to cause gas porosity. The piston velocity of the slow stage should not be too high; otherwise, it would cause air entrainment. The influence of the pressure maintaining time is not obvious due to the ingate solidifying prematurely. The recommended process parameters are a melt injection temperature of 660–680 °C, a piston velocity of 0.1–0.2 m/s in the slow stage, and a piston velocity 2.4–3.2 m/s in the fast stage. This also suggests that appropriate technology should be adopted to delay the solidification time of the ingate in order to realize the feeding effect of pressurization.

Laser cladding technology is an effective method for producing wear-resistant coatings on damaged substrates, improving both wear and corrosion resistance, which extends the service life of components. However, the fabrication of hard and brittle materials is highly susceptible to the problem of cracking. Using gradient transition layers is an effective strategy to mitigate the challenge of achieving crack-free laser-melted wear-resistant coatings. This study presents the cracking issue of laser cladding Ni60B (NiCrBSi) coatings on 38CrMoAl (18CrNiMo7-6) steel by designing a gradient transition layer infused with varying amounts of Ni powder. We examine how different levels of Ni doping in the transition layer influence the fabrication of the Ni60B coating. The results indicate that the cracking mechanism of Ni60B is primarily due to the brittleness and hardness of the fusion cladding layer, which can result in cold cracks under residual tensile stress. Increasing the nickel content in the transition layer reduces the difference in thermal expansion coefficients between the cladding layer and the substrate. Additionally, the nickel in the transition layer permeates the cladding layer due to the laser remelting effect. The physical phase within the cladding layer transitions from the initial CrB, M₇C₃, and γ-Ni solid solution to γ-Ni solid solution and Ni-B-Si eutectic, with a small amount of boride and carbide hard phases. As the nickel doping in the transition layer increases, the proportion of the toughness phase dominated by Ni elements significantly rises, leading to a decrease in the hardness of the fused cladding layer. However, the average hardness of the fusion cladding layer in crack-free samples was measured at 397.5 ± 5.7 HV_0.2, which is 91% higher than that of the substrate.

The flow characteristics during decomposition of hydrate-bearing sediments are the most critical parameters for the gas recovery potential from natural gas hydrate reservoirs. The absolute and relative permeability and the flow field distribution during the decomposition process of hydrate-bearing porous media synthetically created by glass beads are in-situ measured by using magnetic resonance imaging. The absolute permeability value increased slowly, then became stable after the decomposition amount was 50%. The relative permeability change curve is a typical X-shaped cross curve. As the hydrate decomposed, the relative permeability values of the two phases increased, the range of the two-phase co-infiltration zone increased with the increase of relative permeability at the endpoint, and the coexistence water saturation decreased. At the beginning of the decomposition, (hydrate content 100% to 70%), the relative permeability of methane and water rose rapidly from 22% to 51% and from 58% to 70%, respectively. When the amount of the remaining hydrate was less than 50%, the relative permeability curve of the hydrate-bearing glass beads almost kept unchanged. During the hydrate decomposition process, the velocity distribution was very uneven and coincided with the porous media structure.

Bimetals have broad application prospects in many fields due to the combination of the performance characteristics of the two materials, but weak interface bonding limits their promotion and application. Therefore, studying the interfacial behavior to achieve bimetallic strengthening is the focus of this field. However, it is often difficult or costly to visually observe the interfacial behavior using traditional experimental methods. Molecular dynamics (MD) is an advanced microscopic simulation method that can conveniently, rapidly, accurately and intuitively study the diffusion and mechanical behavior at the bimetallic interfaces, providing a powerful tool and theoretical guidance to reveal the nature of interfacial bonding and the strengthening mechanism. This paper summarizes the research progress on molecular dynamics in the bimetallic formation process and mechanical behavior, including Al/Cu, Al/Mg, Al/Ni, Al/Ti, Al/Fe, Cu/Ni, and Fe/Cu. In addition, the future development direction is outlined to provide theoretical basis and experimental guidance for further exploring the formation process and performance enhancement of the bimetallic interfaces.