Efeito da adição de elementos ternarios na microestrutura e propriedades do composito in situ Ni-Ni3Si

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

The fabrication of the structural components for the application in high temperatures and aggressive environments requires the use of materials that retain their chemical, mechanical and physical properties within the proper limits, even above 1000°C. In diverse systems, eutectic structure exhibits inherent thermal stability and permits obtaining an in situ composite, with the aligned and finely dispersed structure, directly from the melt through the directional solidification technique. In the present work, alloys from the Ni-Si and Ni-Si- X (Nb, AI, Cu) were obtained and processed. Initially, samples from these systems were analyzed with regards to solidification microstructure in as-cast condition by using conventional metalographics techniques, with the objective to identify compositions related to eutectic structures. Subsequently, such alloys were directionally solidified using Bridgman tec1mique in an inductive heating furnace. Alloy characterization included, besides the optical and scanning electron microscopy, the use of thermal analysis techniques, X-ray diffraction, mechanical tests like micro hardness, compression and tension, as well as fractography. The obtained results indicated that the directional solidification of the Ni-NhSi eutectic results in a regular microstructure with lamellar morphology, aligned with the direction of heat extraction. Mechanical testing showed that a high strength composite material with a satisfactory ductility was obtained. The fracture surface analysis revealed that these alloys fracture transgranularly in a fragile mode

ASSUNTO(S)

solidificação compostos intermediarios materiais compostos microestrutura

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