Microstructure analysis on IN 718 alloy round rod by FEM in the hot continuous rolling process

Based on physical metallurgy rules and experiential equations, models for microstructure analysis on IN 718 alloy in the round rod hot continuous rolling process has been developed using the finite element method (FEM) on the software ANSYS/LS-DYNA. The dynamic and metadynamic recrystallization models in and after deformation, the grain growth models in the compensated reheating process for IN 718 alloy are regressed, and corresponding processes are involved in these models. For a real rolling practice, the calculated central grain sizes were examined and are in good agreement with the measured ones. The element in the center of the workpiece is a typical one possessing the maximum of the effective strain, the temperature and the grain size in the rolling process. In the hot continuous rolling process, the relationship between the final grain size of the typical element and the inlet velocity of the first stand has been regressed by FE analysis, and the lower rolling speed is beneficial to the grain refinement.     

ITER校正场底部线圈结构的有限元分析

采用有限元法(FEM)研究了ITER装置中超导校正场底部线圈 (BCC)结构的力学性能。针对BCC结构各组合部件三个方向尺寸的巨大差异,将BCC结构均匀化模型和局部细化模型分步组合,通过有限元分析获得了整体结构和薄弱部位各材料的位移场和应力场。针对BCC结构提出了支撑部位螺栓中预紧力的确定方法,用有限元法得出合理的螺栓预紧力,可用于指导BCC结构的安装。     

Effect of simultaneous helium implantation on the microstructure evolution of Inconel X-750 superalloy during dual-beam irradiation

This study focuses on investigation into the effect of helium implantation on microstructure evolution in Inconel X-750 superalloy during dual-beam (Ni⁺/He⁺) irradiation. The 1 MeV Ni⁺ ions with the damage rate of 10^?3 dpa/s as well as 15 keV He⁺ ions using rate of 200 appm/dpa were simultaneously employed to irradiate specimens at 400 °C to different doses. Microstructure characterization has been conducted using high-resolution analytical transmission electron microscopy (TEM). The TEM results show that simultaneous helium injection has significant influence on irradiation-induced microstructural changes. The disordering of γ′ (Ni₃ (Al, Ti)) precipitates shows noticeable delay in dose level compared to mono heavy ion irradiation, which is attributed to the effect of helium on promoting the dynamic reordering process. In contrast to previous studies on single-beam ion irradiation, in which no cavities were reported even at high doses, very small (2–5 nm) cavities were detected after irradiation to 5 dpa, which proved that helium plays crucial role in cavity formation. TEM characterization also indicates that the helium implantation affects the development of dislocation loops during irradiation. Large 1/3 〈1?1?1〉 Frank loops in the size of 10–20 nm developed during irradiation at 400 °C, whereas similar big loops detected at higher irradiation temperature (500 °C) during sole ion irradiation. This implies that the effect of helium on trapping the vacancies can help to develop the interstitial Frank loops at lower irradiation temperatures.     

Ballistic performance of novel design of bulletproof plates inspired by biomimetic approaches

Metal and polymer matrix composite materials are preferred in bulletproof applications due to their high-impact resistance and lightness. Personal/demand-specific designs that have become possible with the developing additive manufacturing technologies have brought a new perspective to armor technologies. At the same time, parts with complex structures designed with biomimetic approaches can be easily manufactured with additive manufacturing. In this study, biomimetic armors obtained from standard Carbon fiber reinforced polymer (CFRP) and Inconel 718 materials were compared with traditional armor structures. Within the scope of the study, 9 × 19 mm² parabellum and 7.62 mm NATO bullets were impacted at 275 m/s and 600 m/s speeds on biomimetic and conventional armor consisting of three and five layers. Bullet velocities during impact, deformation of bullets, deformation of armor, and harmonic behavior are discussed. The results obtained were also used to calculate the damped impact energies. In the study, it was determined that biomimetic plates could absorb 22%–38% more impact energy. It has been determined that CFRP materials can absorb 45% more impact energy compared to Inconel 718.