Tecnologia em Metalurgia, Materiais e Mineração
https://www.tecnologiammm.com.br/doi/10.4322/2176-1523.20191697
Tecnologia em Metalurgia, Materiais e Mineração
Artigo Original

INFLUÊNCIA DA COMPOSIÇÃO QUÍMICA, POROSIDADE E ENVELHECIMENTO NAS PROPRIEDADES MECÂNICAS DE LIGAS AL-SI-MG FUNDIDAS

INFLUENCE OF CHEMICAL COMPOSITION, POROSITY AND AGING IN THE MECHANICAL PROPERTIES OF AL-SI-MG ALLOYS

Albino Moura Guterres, Claudio André Lopes de Oliveira, Carlos Alexandre dos Santos

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Resumo

O objetivo do presente trabalho foi analisar a influência da composição química, porosidade e efeitos dos tratamentos térmicos em algumas propriedades mecânicas em ligas de Al-Si-Mg fundidas. Duas ligas de Al-3,8%Si-0,25%Mg (Liga I) e Al-6,5%Si-0,6%Mg (Liga II) foram preparadas, fundidas e solidificadas em molde metálico, com e sem processo de desgaseificação. Amostras foram obtidas para análises do percentual de porosidade e determinação das propriedades mecânicas. Parte das amostras foram submetidas a tratamentos térmicos de endurecimento por precipitação. Em relação à porosidade, observou-se que a Liga II apresentou maior percentual de porosidade por conter mais Si e Fe na sua composição química. Após as análises das propriedades mecânicas, observou-se que, com a aplicação do tratamento térmico, a Liga II apresentou os melhores resultados, gerando aumento de 25% na resistência à tração e 23% na dureza. Na análise da correlação da composição química, percentual de porosidade e efeitos dos tratamentos térmicos com a variação nas propriedades mecânicas, modelos matemáticos que permitem prever o limite de resistência à tração e dureza nestas ligas foram desenvolvidos.

Palavras-chave

Ligas de Al-Si-Mg; Endurecimento por precipitação; Porosidade; Propriedades mecânicas.

Abstract

The main objective of this work was to analyze the influence of chemical composition, porosity and the effects of heat treatments on some mechanical properties in the Al-Si-Mg as-cast alloys. Two alloys of Al-3,8% Si-0,25% Mg (Alloy I) and Al-6,5% Si-0,6% Mg (Alloy II) were prepared, cast and solidified in metal mold, with without degassing process. Samples were extracted for percentage of porosity analysis and mechanical properties determination. Part of the samples were subjected to precipitation hardening heat treatments. In relation to the porosity, it was observed that the alloy II presented higher percentage of porosity because it contained more Si and Fe in its chemical composition. Regarding mechanical properties analyses, the alloy II presented the best results, resulting in an increase of 25% in the tensile strength and 23% in the hardness when heat treatment was applied. In the analysis of the correlation between chemical composition, percentage of porosity and the effects of the heat treatments with the variation in the mechanical properties, it was developed mathematical models that allow to predict the tensile strength and hardness in these Al-Si-Mg alloys.

Keywords

Al-Si-Mg alloys; Precipitation hardening; Porosity; Mechanical properties.

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