EBSD-data analysis of an additive manufactured maraging 300 steel submitted to different tempering and aging treatments

This research was funded by FAPESP grants (2017/17697-5, 2019/00691-0, and 2020/09079-2) and was supported by LNNano – Brazilian Nanotechnology National Laboratory (CNPEM/MCTI) during the use of the electron microscopy open access facility. F. Conde acknowledges the Ph.D. scholarship CNPq 142440/2019-1. In addition, JPO acknowledges funding by national funds from FCT - Fundação para a Ciência e a Tecnologia, I.P., in the scope of the projects LA/P/0037/2020, of the Associate Laboratory Institute of Nanostructures, Nanomodelling, and Nanofabrication – i3N. Finally, Julian A. Avila is a Serra Hunter Fellow and a CNPq fellow. Publisher Copyright: © 2023 The AuthorsMaraging is a high alloy steel sensitive to the precipitation of intermetallics from a supersaturated solid solution during aging heat treatments. The precipitation phenomenon is well described in the literature, which gave rise to the alloy name regarding a martensite matrix with precipitates formed by aging treatment. Many studies have been performed to characterize this material, usually subjected to many sample preparations for transmission microscopy, which is very laborious, and few EBSD analyses. Therefore, in this work, a large study was conducted using electron backscatter diffraction (EBSD) to analyze maraging microstructures through band-contrast, kernel average misorientation (KAM), grain orientation spread (GOS), and misorientation distribution. Our results show that solubilization of the additive manufactured maraging steel resulted in a more homogeneous microstructure with new angle grain boundaries. Furthermore, tempering heat treatments relieve martensite strain, increasing band contrast values. Posterior aging presented a low impact on the results of EBSD analysis.publishersversionpublishe

Broadband terahertz pulse generation driven by an ultrafast thin-disk laser oscillator

We demonstrate broadband THz generation driven by an ultrafast thin-disk laser (TDL) oscillator. By optical rectification of 50-fs pulses at 61 MHz repetition rate in a collinear geometry in crystalline GaP, THz radiation with a central frequency at around 3.4 THz and a spectrum extending from below 1 THz to nearly 7 THz are generated. We realized a spectroscopic characterization of a GaP crystal and a benchmark measurement of the water-vapor absorption spectrum in the THz range. Sub-50-GHz resolution is achieved within a 5 THz bandwidth. Our experiments show the potential of ultrafast TDL oscillators for driving MHz-repetition-rate broadband THz systems

Ethanol Steam Reforming for Hydrogen Production in Microchannel Reactors: Experimental Design and Optimization

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)In this investigation, an experimental design procedure using prior literature information has been used to guide the localization of optimal points for reaction kinetics study. Three kinetic models were identified and the Pareto domain was circumscribed for a set of three decision variables and two objective functions to find an optimal solution. From the range of Pareto-optimal solutions obtained, the kinetic model considered to be the most reliable was used to explore the optimal operating region. Finally, the experimental design points were chosen to ensure a sufficient range of operating conditions to identify the reaction kinetics.o TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE AGOSTO DE 2015.11Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Ductility Improvement Due To Martensite α' Decomposition In Porous Ti-6al-4v Parts Produced By Selective Laser Melting For Orthopedic Implants.

Ti-6Al-4V parts obtained by selective laser melting typically have an acicular α' martensitic microstructure whose ductility is low. Thus, post-heat treatments are useful for increasing ductility. In this work, the effects of sub-β-transus heat treatments on the mechanical properties of Ti-6Al-4V parts with porous structures are correlated with martensite α' phase decomposition. The precipitation of β phase and the gradual transformation of α' into α phase by the diffusion of excess vanadium from α' to β phase are proposed to be the main events of martensite α' phase decomposition in parts fabricated by selective laser melting. The heat treatment performed at 650°C for 1h produced no microstructural changes, but the samples treated for at the same temperature 2h showed a fine precipitation of β phase along the α' needle boundaries. The heat treatment performed at 800°C for 1 or 2h produced a fine α+β microstructure, in which β phase are present as particles fewer in number and larger in size, when compared with the ones present in the sample heat-treated at 650°C for 2h. Heat-treatment of the parts at 800°C for 2h proved to be the best condition, which improved the ductility of the samples while only slightly reducing their strength.54149-15

Spinning reserve opportunity cost in hydroelectric plants

Starting from the deregulated process of the Electric Sector, there was the need to attribute responsibilities to several agents and to elaborate appropriate forms of remuneration of the services rendered by the same. One of the services of great importance within this new electric sector is the Ancillary Services. Among the various types of Ancillary Services, Spinning Reserve is a service necessary for maintaining the integrity of the transmission system from either generation interruptions or load variations. This paper uses the application of the Economic Dispatch theory with the objective of quantifies the availability of Spinning Reserve supply in hydroelectric plants. The proposed methodology utilizes the generating units as well as their efficiencies so as to attend the total demand with the minimum water discharge. The proposed methodology was tested through the data provided by the Água Vermelha Hydroelectric Power Plant. These tests permitted the opportunity cost valuation to the Spinning Reserve supply in hydroelectric plants. © 2005 IEEE