Influência na microestrutura e propriedades mecânicas da liga de alumínio A380 fundida sob pressão pela variação nas velocidades de injeção
Influence in the microstructure and mechanical properties of the aluminum alloy A380 die casting by the injection speed steps
Carlos Alberto Marchioli, Gisele Fabiane Costa Almeida, Rodolfo Luiz Prazeres Gonçalves, Marcos Domingos Xavier, Givanildo Alves dos Santos, Antonio Augusto Couto
Resumo
Na fundição sob pressão de ligas de alumínio, devido à alta velocidade de injeção do metal líquido no molde, obtém-se uma microestrutura com grãos refinados e possível ocorrência de defeitos como microporosidade e microrechupes. Esses defeitos podem ocorrer devido a deficiências no projeto do ferramental, na definição dos parâmetros de cálculo ou mesmo no controle dos parâmetros de injeção. O objetivo deste trabalho é analisar a influência das velocidades das fases de injeção (primeira e segunda fases) na microestrutura e propriedades mecânicas da liga de alumínio A380. Corpos de prova foram moldados sob pressão de matriz em uma máquina de injeção de câmara fria. A faixa de velocidade de injeção do processo foi de 0,10 m/s, 0,25 m/s e 0,50 m/s para a primeira fase, e 0,6 m/s, 1,5 m/s 3,0 m/s para a segunda fase. As propriedades mecânicas foram determinadas por meio de ensaios de tração e dureza e a caracterização microestrutural por microscopia óptica. Os resultados indicaram que a velocidade de injeção não influencia o limite de resistência tanto da primeira quanto da segunda fase de injeção. No entanto, o nível de porosidade e erros de execução mudaram em função das variações de velocidade, fatores que afetam o resultado do alongamento e limite de escoamento dos produtos de fundição sob pressão.
Palavras-chave
Abstract
In pressure die casting, due to the high speed of the liquid metal injection into the mold, a microstructure with refined grains is obtained and defects such as microporosity and microshrinkage, cold shut, and misrun can occur. These defects can occur due to deficiencies in the tooling design (injection mold), in the definition of calculation parameters, or even in the control of the injection parameters. The aim of this paper is to analyze the influence of injection phase velocities (first and second phases) on the microstructure and mechanical properties of the Aluminum A380 alloy. Standard test samples were cast under die pressure in a cold chamber injection machine. The range injection speeds of the process were 0.10 m/s, 0.25 m/s and 0.50 m/s for the of the first phase, and 0.6 m/s, 1.5 m/s 3.0 m/s of the second phase. The mechanical properties characterization was performed by tensile and hardness tests and the microstructural characterization by optical microscopy. The results indicated that the injection speed does not influence the strength limit of both the first and the second injection phases. However, the level of porosity and misruns changed as a function of the speed variations, factors that affect the result of the elongation and yield point of the die-casting products.
Keywords
Referências
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Submetido em:
01/10/2022
Aceito em:
05/12/2022
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