Solid State Phenomena Vol. 315

Abstract: Ti-Mo-based alloy ingots with different chemical compositions are melted in a vacuum arc furnace under argon atmosphere. The specimens are annealed or water quenched. Heat treatments were carried out in tube-furnace under argon atmosphere. X-ray diffraction (XRD) experiments were performed using a X-ray diffraction apparatus in order to detect the phase constitutes and microstructures of the Ti-Mo-based specimens.

Abstract: In order to investigate the relation between prior austenite grains (PAG) and the carbide particles, we observed etched microstructure in JIS-SUJ2 steel. We traced and drew the outlines of carbide particles and analyzed some of their shape values. We confirmed that the repeated quenching can refine PAG size while keeping the optimal distribution of the carbide particles.

Abstract: In order to investigate the wear behavior of induction-heated 13Cr-2Ni-2Mo stainless steel, we performed the rolling contact fatigue (RCF) tests in water. We interrupted the RCF test at each 1.0×10⁵ cycles and measure the wear loss and observed the contact surface. After the RCF tests, we found the oxygen concentration area in the contact area.

Abstract: In this work, an experimental measurement, contour method, is implemented for an after quenching IN718 forging specimen to obtain the distribution of residual stress field. A sequentially coupled thermal mechanical finite element model is developed with the similar 3D geometry of the experimental specimen and implemented the same heat transfer boundary of the rapid quenching with the experimental condition. A thermal mechanical rate dependent continuum plasticity model for IN718 alloy, with the dynamic strain ageing (DSA) effect incorporated, is developed to study the impact of DAS effect on the evolution of residual stress during rapid quenching. The modelling predictions of residual stress are in good agreement with the contour method measurements. The impact of DSA effect is further quantified, indicating that an annular high plastic strain rate region in the core part of the disc is captured during the simulation of the quenching process.

Abstract: In this paper, a micromechanical finite element (FE) model has been proposed to investigate the effect of the nanoscale precipitates on the development of microplasticity for Inconel 718 (IN718) superalloy. A strain gradient crystal plasticity formulation has been developed with the considerations of the evolution of statistically stored dislocation density and geometrically necessary dislocation density. The mesh convergence has been examined, showing that sufficiently fine mesh is required in the FE model. The results show that the model with strain gradient effect incorporated shows less peak plastic strain and higher value of dislocation density than the model with no strain gradient effect. The present study indicates that the strain hardening process at the scale of strengthening precipitate is mainly governed by the evolution of geometrically necessary dislocation densities.

Abstract: Through hyperworks and Lsdyna, the side impact simulation of the vehicle model with Q&P980 class B-pilla is carried out. The middle part of B-pillar is the main part to bear the impact load, which corresponds to the occupant's chest and abdomen. The invasive displacement and the speed are large and the change trend is basically the same. After the optimization of the B-pillar weld solder joint layout, the number of solder joints was reduced by 23.61%, the structural static stiffness and the first-order torsional frequency were improved, the collision performance remained basically unchanged, and the body assembly cost was reduced.

Abstract: 2.25Cr1Mo0.25V steel has better high temperature strength than ordinary Cr-Mo steel, and has been widely used in nuclear and chemical environments such as nuclear energy and chemical industry. However, vanadium-added steel is still likely to cause hydrogen damage and requires early detection. Ultrasonic inspection has strong penetrating ability. It can detect thin plates with thickness of 1-2mm and steel structure of several meters long. In this paper, ultrasonic longitudinal wave was used to detect the amplitude and longitudinal wave period before and after hydrogen charging, and the change of wave velocity was obtained. The dynamic tensile test of the specimen before and after hydrogen charging was also carried out, and the elastic modulus and elongation of hydrogen before and after hydrogen charging were obtained. The relationship between ultrasonic signal and hydrogen embrittlement was also discussed in this paper.

Abstract: A new generation of electron beam tool for welding during assembly and repair-restoration works on board of manned space vehicles in open space was demonstrated. The tool includes a small-sized electron beam gun (EBG) with an electron beam power of up to 2.5 kW and a high-voltage power source with a voltage of 10 kV. The design of the electron-optical system of EBG allows using it in both manual as well as in automatic mode applying robotic devices. Applying the manufactured EBG and manipulator, in vacuum chamber the works on simulating the repair of a spacecraft’s section of aluminum 2219 alloy were carried out. The obtained results of studying the structure and mechanical characteristics and also sealing of welds confirmed the high quality of welded joints and a reliability of the technology for repairing a damaged fragment of a spacecraft's body using electron beam welding.

Abstract: Cerium oxide (CeO₂) is one of potential candidates of hydrophobic coatings servicing in harsh environments. In this letter, abraded CeO₂ surface was prepared using sandblasting treatment to investigate the wetting mechanism under the condition of impact abrasive wear. The water contact angle (WCA) of the abraded surface increased from 62.8° to 93.7° after aging in ambient air for about 700 h. The hydrophobic self-optimisation mechanism of the abraded CeO₂ surface is due to the hierarchical structure formed during impact abrasive wear and the surface adsorption of airborne hydrocarbon, resulting the wetting state changed from “Wenzel state” to “Cassie-Baxter State”.

Abstract: This paper focuses on the preparation of High Density Polyethylene/Poly (Vinyl Alcohol) Fiber composites which was fabricated via melt blending/compounding method using a Laboratory Mixing Extruder (LME). The effect of PVA fiber concentrations (i.e. 0, 5, 10, 20, 30 wt%) on the thermal properties (i.e. melting and crystallization) of the composites was investigated. The thermal properties of the composites were analysed using a Differential Scanning Calorimetry (DSC). The DSC analysis results exhibited that the presence of PVA fiber did not considerably change the melting and crystallization properties of the composites. The melting temperature (Tm) of all the composites samples were similar, which was in the range of 130 - 131 °C. The highest Tm was belong to sample PVAC-20 (i.e. 20 wt% PVA fiber). In the other hand, the crystallinity index (Xc) of the HPDE/PVA fiber composites decreased with the increase of PVA fiber concentrations. The Xc of the composites decreased from 56.7 % for PVAC-0 to 49.8 % for PVAC-20. Additionally, in term of crystallization behavior of the composites, the effect of PVA loadings on the crystallization temperature (Tc) of the composites was also not significant. The Tc of all composites samples were similar, which was about 115 °C. It can be suggested that the addition of PVA fiber did not affect the crystallization process of the matrix.