Xiang Zan

A common issue encountered in metal powder injection molding is the separation of the powder and binder during the injection process, which can give rise to a number of defects. In order to investigate the phenomenon of phase separation in stainless-steel injected flat parts, a numerical simulation methodology was employed by using the Moldex3D R14.0 finite element software to simulate the injection process. Then, the impact of injection parameters on separation was analyzed by comparing key performance indicators such as powder volumetric concentration and density. Furthermore, the extent of the separation was minimized by the optimization of process parameters. The simulation results indicate that the separation of binder and powder is most severe near the gate, where the binder percentage is the highest. The application of elevated mold temperatures, augmented injection rates and reduced injection temperatures can effectively mitigate the two-phase separation phenomenon and enhance the uniformity of powder distribution. This provides a crucial theoretical foundation and technical support for the enhancement of the quality and performance of metal powder injection products.

The microstructure of and damage to the upper divertor components in EAST were characterized by using metallography, EBSD, and SEM. Under the synergistic effect of heat load and plasma irradiation, cracking, recrystallization, and interface debonding were found in the components of the upper divertor target. The crack propagates downward from the heat loading surface along the heat flux direction, and the crack propagation mode is an intergranular fracture. The thermal loads deposited on the edge of monoblocks raise the temperature higher than the recrystallization temperature of pure tungsten, and the microstructure changes from being in a rolled state to being recrystallized. Additionally, cracks exist in both recrystallized and rolled areas. EBSD boundary maps show that the range of the recrystallization area is determined via the heat flux distribution. The Cu/CuCrZr interface of the cooling components near the thermal loading area is debonded, and the structural integrity is destroyed.

Tungsten and its alloys are considered to be the most nominated plasma-facing materials in fusion reactors, which will be exposed to enormously rigorous conditions such as thermal load, plasma exposure, and neutron radiation. At present, the research on the behavior of oxide particle-reinforced tungsten-based materials under long-term steady-state heat load and transient thermal shock is insufficient. The purpose of this study is to investigate the performance of yttria particle-reinforced tungsten plates prepared by the wet chemical method under heat loads by means of indirect coupling experiments. An Nd:YAG laser device is used to perform thermal shock events. The surface damage and microstructure evolution of rolled and fully recrystallized samples exposed to laser thermal shock are observed and analyzed. The cracking threshold of the rolled and fully recrystallized samples is about 0.40~0.48 GW/m²; the degree of surface damage of them aggravates with the increased laser power density. What is more, cracks or even melting damage could be observed on the surface and be accelerated by the process of recrystallization, resulting in the degradation of the ability to withstand the thermal shock of the material.