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Microstructure modelling of laser metal powder directed energy deposition of Alloy 718
摘要： A multi-component and multi-phase-field modelling approach, combined with transformation kinetics modelling, was used to model microstructure evolution during laser metal powder directed energy deposition of Alloy 718 and subsequent heat treatments. Experimental temperature measurements were utilised to predict microstructural evolution during successive addition of layers. Segregation of alloying elements as well as formation of Laves and δ phase was specifically modelled. The predicted elemental concentrations were then used in transformation kinetics to estimate changes in Continuous Cooling Transformation (CCT) and Time Temperature Transformation (TTT) diagrams for Alloy 718. Modelling results showed good agreement with experimentally observed phase evolution within the microstructure. The results indicate that the approach can be a valuable tool, both for improving process understanding and for process development including subsequent heat treatment.
关键词： Modelling,Heat Treatment,Phase-field,Thermal Cycle,DED
更新于2025-11-21 11:18:25
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[IEEE 2018 IEEE 4th International Forum on Research and Technology for Society and Industry (RTSI) - Palermo, Italy (2018.9.10-2018.9.13)] 2018 IEEE 4th International Forum on Research and Technology for Society and Industry (RTSI) - Structural and Optical Behaviour of MAPbI<inf>3</inf> Layers in Nitrogen and Humid Air
摘要： The tendency of MA+-containing perovskites to degradation under humid air is still the main challenge which limits the durability of technologies. We indeed frame the behavior of MAPbI3 layer through structural and optical characterization under thermal cycles and using the environmental composition as a variable parameter (humid air, N2, Ar, O2). Within the temperature range explored (RT-80°C) we likely approach the thermal operation of the material under the sun and find that the degradation mechanism is linked to the action of water molecules by the formation of lattice defects. They rise the lattice disorder, especially at the crossover of the tetragonal to cubic transition wherein an acceleration of the degradation kinetics is observed. Nitrogen can help rationalizing solutions to stabilize the materials even at this critical transition step, since it behaves as more than an inert species.
关键词： Spectroscopic Ellipsometry,Photovoltaics,X-ray diffraction,Hybrid Perovskites,Stability,Thermal Cycle
更新于2025-09-23 15:22:29
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Influence of process parameters on thermal cycle and intermetallic compounds formation in high speed laser weld-brazing of aluminium-steel angle joints
摘要： AA6016-T4 aluminium and DX56D+Z140M steel sheets were joined by fluxless laser weld-brazing process with ER4043 AlSi5 filler wire at high brazing speed. The configuration studied corresponds to typical automotive roof/body-side angle joints. At the interface, the measurements of thermal cycle are performed with K-thermocouples. The results are compared to simulated thermal cycles obtained through SYSWELD Software. Thermal cycles are evaluated with the maximal temperature reached, the time of interaction at high temperature and the cooling speed. Several combinations of laser power and brazing speed are both investigated experimentally and by simulation to study their influence on the thermal cycle and the intermetallic layer thickness. Thermal cycles are discretized to calculate the theoretical growth of the intermetallic compounds with a diffusion-based model. The result is compared to experimental intermetallic layer measured with optical microscopy. The power tends to influence both the maximal temperature and the cooling speed whereas the brazing speed only influences the maximal temperature. The calculation demonstrates the capability to distinguish the process configuration which will lead to the thickest intermetallic layer.
关键词： fluxless laser weld-brazing,simulation,Fe-al dissimilar joints,intermetallic layer calculation,thermal cycle,process parameters
更新于2025-09-12 10:27:22
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Experimental study of observed defects in mini-modules based on crystalline silicone solar cell under damp heat and thermal cycle testing
摘要： In this study, consumer type multicrystalline modules are investigated. To assess the long-term reliability of photovoltaic (PV) multicrystalline modules, extended thermal cycling and damp heat testing were performed. This study focused on four multicrystalline modules. Two modules were subjected to 85 °C/85% damp heat testing at 1000 h and 1300 h, respectively. The other two modules were subjected to thermal cycle test of 55 cycles and 66 cycles, respectively. After testing, all 4 solar panels were investigated with the help of visual inspection, thermography, electroluminescence and IV-curve measurements. The main degradations observed were corrosion, hot spot and delamination.
关键词： Thermal cycle,Degradation,Mini-module,Damp-heat
更新于2025-09-12 10:27:22