Obtenção e caracterização de compostos do tipo in situ no sistema A1 Nb

AUTOR(ES)
DATA DE PUBLICAÇÃO

1994

RESUMO

This work analyses the feasibility of in situ composites production in the AI-Nb system, containing AI- fhase as matrix and intermetallic NbAl3 as reinforcement; and characterizes 6, 12 and 18%vol NbAl3 produced composites in relation to their mechanical properties (hardness; yield strength, ultimate tensile strength, strain; wear), thermal expansion and density. Two different processes were tested to produce such composites: by melting together AI and Nb and by dissolution of Nb in liquid AI. The first process was considered inadequate due to volume of material limitations and to the unproper morphology of the resulting intermatallics. Composites showing polygonal intermetallic particles as reinforcement, reasonably distributed in the matrix were obtained from mas ter alloys produced by Nb dissolution in AI. Dissolution mechanisms were analysed in order to allow control of the reinforcement particle morphology. Produced composites showed increasing Brinell hardness as fraction of reinforcement increases as much as 80% to the hardness of the commercial AI used as matrix. Yield strength at room temperature was also increased up to 62% higher in the composites related to AI; ultimate tensile strength increased to 50% and strain reduced to 90% in the composites when compared to the matrix. Tension tests carried out at 150C also gave interesting results: 85% increasing on ultimate tensile strength, up 93% increasing on yield strength and 86% reduction of strain for composites, compared to values for AI. In general, modifications on properties increased as reinforcement volume fraction increased. Micromechanisms of ductile fracture were observed in the composites. Concerning to wear properties, composites showed wear rates up to 70% smaller than AI. Deformation and fragmentation were the dominant wear mechanisms for composite material. Composites showed also superior quality related to thermal stability: expansion till 13% lower than the value obtained for AI was observed. Also in this case, increasing amount of particles lead to more severe alterations in the property. Apparent density of composites were also dependent on NbAl3 volume fraction, maximum volume of 14% higher than AI density was obtained for the richest composite. General results enable to present a new, characterized material, together with a fabrication method and suggestions for its application

ASSUNTO(S)

engenharia de produção compositos polimericos

ACESSO AO ARTIGO

Documentos Relacionados