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
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
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
Referências
1 Gopikrishna S, Binu CY. Study of effects of T6 heat treatment on grain refined A319 alloy with magnesium and strontium addition. International Journal on Theoretical and Applied Research in Mechanical Engineering. 2013;2(3):59-62.
2 Serrano-Munoz I, Buffiere JY, Verdu C, Gaillar Y, Mu P, Nadot Y. Influence of surface and internal casting defects on the fatigue behaviour of A357-T6 cast aluminium alloy. International Journal of Fatigue. 2016;82(3):361-370.
3 Kaeel AJ. Study the effect of solution treatment on mechanical properties of Al-7%\Si-0.3%Mg alloy. Natural and Applied Sciences. 2013;4:76-85.
4 ASM International. ASM Handbook Casting. Vol. 15, 9th. Ohio: AST International; 2002. Edition Metals Handbook.
5 Manente A, Timelli G. Optimizing the heat treatment process of cast aluminium alloys. INTECH Open Access Publisher. 2011;9:197-220.
6 Dioni D, Cecchel S, Cornacchia G, Faccoli M, Panvini A. Effects of artificial aging conditions on mechanical properties of gravity cast B356 aluminum alloy. Transactions of Nonferrous Metals Society of China. 2015;25(4):1035-1042.
7 Shabani MO, Mazahery A. Prediction of mechanical properties of cast a356 alloy as a function of microstructure and cooling rate. Archives of Metallurgy and Materials. 2011;56(3):671-675.
8 Dobrzanski LA, Borek W, Maniara R. Influence of the crystallization condition on Al-Si-Cu casting alloys structure. Journal of Achievements in Materials and Manufacturing Engineering. 2006;18:211-214.
9 Puparattanapong K, Limmaneevichitr C. Effect of scandium on porosity formation in Al–6Si–0.3Mg alloys. The Indian Institute of Metals – IIM. 2016;69:1-8.
10 Bueno AW, Degreve L. Manual de laboratório de físico-química. São Paulo: McGraw-Hill; 1980.
11 Moutinho DJC. Análise da evolução microestrutural e da formação de macrossegregação e microporosidade na solidificação unidirecional transitória de ligas ternárias Al-Cu-Si [tese]. Campinas: Universidade Estadual de Campinas; 2012.
12 ASTM International. ASTM Standart B311-93 - Test Method for Density Determination for Powder Metallurgy (P/M) Materials Containing Less Than Two Percenty Porosity. West Conshohocken: ASTM International.
13 Ashby MF, Jones DRH. Engineering materials 1: an introduction to properties, applications and design. 3rd ed. Oxônia: Butterworh Heinemann; 2005.
14 ASTM International. ASTM E8M-04 - Standard Test Methods for Tension Testing of Metallic Materials. West Conshohocken: ASTM International; 2004.
15 Associação Brasileira de Normas Técnicas. ABNT NBR NM ISO 6506-1:2010 - Materiais metálicos – ensaio de dureza Brinell. Rio de Janeiro: ABNT; 2010.
16 Patakham U, Kajornchaiyakul J, Limmaneevichitr C. Modification mechanism of eutectic silicon in Al–6Si–0.3 Mg alloy with scandium. Journal of Alloys and Compounds. 2013;575:273-284.
17 Dong QZ, Choi YS, Hong JH, Hwang HY. Prediction of mechanical properties of Al alloys with change of cooling rate. Overseas Foundry. 2012;9(4):671-675.
18 Moustafa MA. Effect of iron content on the formation of β-Al5FeSi and porosity in Al–Si eutectic alloys. Journal of Materials Processing Technology. 2009;209(1):605-610.
19 Gomes LG. Microestrutura dendrítica, macrossegregação e microporosidade na solidificação de ligas ternárias Ai-Si-Cu [tese]. Campinas: Universidade Estadual de Campinas; 2012.
20 Dwivedi DK, Sharma R, Kumar A. Influence of silicon content and heat treatment parameters on mechanical properties of cast Al–Si–Mg alloys. International Journal of Cast Metals Research. 2013;19(5):275-282.
21 Rana RS, Purohit R, Das S. Reviews on the influence of alloying elements on the microstructures and mechanical properties of aluminum alloys and aluminum composites. International Journal of Scientific and Research Publications. 2012;2(6):1-7.
22 Kaygisiz Y, Maraşli N. Microstructural, mechanical and electrical characterization of directionally solidified Al–Si–Mg eutectic alloy. Journal of Alloys and Compounds. 2015;618:197-203.
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