Banca de DEFESA: JONAS MENDES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : JONAS MENDES
DATA : 12/12/2024
HORA: 14:00
LOCAL: meet.google.com/rtv-bqaf-nfq
TÍTULO:

DEVELOPMENT AND CHARACTERIZATION OF MULTI-COMPONENT REFRACTORY ALLOYS BASED ON AlCrNiNbMoW OBTAINED BY POWDER METALLURGY

PALAVRAS-CHAVES:

High entropy alloys, equiatomic and non-equiatomic alloys, Mechanical Alloying, powder metallurgy

PÁGINAS: 158
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Metalurgia Física
ESPECIALIDADE: Estrutura dos Metais e Ligas
RESUMO:

The development of high-entropy alloys has become in recent years as an alternative for producing alloys with enhanced properties. High-entropy alloys are multicomponent alloys composed of five or more main elements in equiatomic or near-equiatomic ratios. The high configurational entropy in a multicomponent alloy, compared to conventional alloys, results in the stabilization of alloying elements in stable solid solutions. Among the groups of multicomponent alloys, refractory high-entropy alloys stands out; they are composed of refractory elements and are considered a significant innovation in the development of materials for high-temperature applications. Thus, these materials must ensure thermal stability, wear resistance, and oxidation resistance at high temperatures and in oxidizing environments. Traditionally, these alloys are produced through melting, one of the most known manufacturing techniques. However, this method increases the probablility of heterogeneous structures with elemental segregation and other crystal defects, such as dislocations and grain boundaries. To solve this troublesome, powder metallurgy will be adopted as an alternative production method. This manufacturing method promotes solubility in the solid state and the formation of homogeneous alloys, providing the final product with properties equivalent to those obtained by melting. Additionally, the process offers significant energy savings, making it a viable alternative to traditional manufacturing methods. Taking into consideration, this work aims to produce and microstructurally characterize five combinations of the refractory multicomponent alloy based on AlCrNiNbMoW, manufactured by powder metallurgy. The atomic proportions of Al and Cr will be varied in 25% increments, from the equiatomic ratio to the total substitution of aluminum by chromium, to evaluate the influence of these variations on phase formation and oxidation resistance. The results revealed that all produced alloys exhibited a similar microstructural composition, characterized by the formation of a solid solution with a BCC crystalline structure and Laves phase. Oxidation tests resulted in the formation of oxides of aluminum, niobium, chromium, and tungsten. The alloy with the lowest mass gain was Al_4.2Cr_29.2, at 0.037 g/cm². The reduction in aluminum content in the produced alloys proved beneficial, as it proportionally decreased the mass gain. The studies carried out in this thesis enable the exploration of the potential of the four high-entropy effects in the design of new refractory multicomponent alloys produced via powder metallurgy, resulting in the formation of solid solutions with a BCC crystalline structure and Laves phase observed through microstructural characterization and X-ray diffraction. This thesis explores the potential of the four high-entropy effects in the development and understanding of new refractory multicomponent alloys produced by powder metallurgy. The studies demonstrate that these alloys form simple solid solutions with a BCC crystalline structure and Laves phase, confirmed by microstructural characterization and X-ray diffraction.

MEMBROS DA BANCA:
Presidente - 1763554 - GEOVANI RODRIGUES
Interna - 1714699 - MIRIAN DE LOURDES NORONHA MOTTA MELO
Externo ao Programa - 2307914 - ANTONIO AUGUSTO ARAUJO PINTO DA SILVA - UNIFEIExterno ao Programa - 3386251 - RICARDO MELLO DI BENEDETTO - UNIFEIExterno à Instituição - GISELE FERREIRA DE LIMA ANDREANI - UNIFESP
Externa à Instituição - KATIA REGINA CARDOSO - UNIFESP