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Corrosion and tribocorrosion behaviour of Al-Si-Cu-Mg alloy and its composites reinforced with B4C particles in 0.05M NaCl solution

Toptan, F.; Alves, A. C.; Kerti, I.; Ariza, E.; Rocha, L. A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 27-35
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The corrosion behaviour of metal matrix composites (MMCs) is strictly linked with the presence of heterogeneities such as reinforcement phase, microcrevices, porosity, secondary phase precipitates, and interaction products. Most of the literature related to corrosion behaviour of aluminium matrix composites (AMCs) is focused on SiC reinforced AMCs. On the other hand, there is very limited information available in the literature related to the tribocorrosion behaviour of AMCs. Therefore, the present work aims to investigate corrosion and tribocorrosion behaviour of Al-Si-Cu-Mg alloy matrix composites reinforced with B4C particulates. Corrosion behaviour of 15 and 19% (vol) B4C reinforced Al-Si-Cu-Mg matrix composites and the base alloy was investigated in 0.05M NaCl solution by performing immersion tests and potentiodynamic polarisation tests. Tribocorrosion behaviour of Al-Si-Cu-Mg alloy and its composites were also investigated in 0.05M NaCl solution. The tests were carried out against alumina ball using a reciprocating ball-on-plate tribometer. Electrochemical measurements were performed before, during, and after the sliding tests together with the recording of the tangential force. Results suggest that particle addition did not affect significantly the tendency of corrosion of Al-Si-Cu-Mg alloy without mechanical interactions. During the tribocorrosion tests...

Effect of Al2Cu precipitates size and mass transport on the polarisation behaviour of age-hardened Al–Si–Cu–Mg alloys in 0.05M NaCl

Vieira, A. C.; Pinto, A. M.; Rocha, L. A.; Mischler, S.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2011 ENG
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The electrochemical behaviour of age-hardened Al–Si–Cu–Mg alloys was investigated in a 0.05 M NaCl solution under controlled mass transport conditions using a rotating disk electrode. This work aimed at getting better understanding of the effect of the alloy microstructure, in particular the size distribution of Al2Cu phase, on the corrosion behaviour of the alloy. Three different size distributions of the Al2Cu phase were obtained through appropriate heat treatments. The cathodic reduction of oxygen was found to occur mainly on the Al2Cu phases acting as preferential cathodes. Small sized Al2Cu phases were found to promote at high rotation rates a transition from a 4 electron to a 2 electron dominated oxygen reduction mechanisms.

Mechanical and electrochemical deterioration mechanisms in the tribocorrosion of Al alloys in NaCl and in NaNO3 solutions

Vieira, A. C.; Rocha, L. A.; Papageorgiou, Nikolaos; Mischler, S.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Artigo de Revista Científica
Publicado em //2012 POR
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Tribocorrosion of Al-Si-Cu-Mg alloys was investigated in 0.05 M NaCl and 0.1 M NaNO3 solutions under severe sliding and controlled electrochemical conditions. A simple galvanic coupling model was developed to analyze and quantitatively predict the evolution potential of the open circuit potential during tribocorrosion. According to this model and the obtained results, galvanic coupling was established in the NaNO3 solution within the wear track between passive and mechanically depassivated areas. In the NaCl solution, galvanic coupling was established between the whole depassivated wear track and the surrounding area. This difference was attributed to different mechanical properties of the passive surfaces.

Changes in the properties of Cu-Al-Mn shape memory alloy due to quaternary addition of different elements

Kumar,Pravir; Jain,Ashish Kumar; Hussain,Shahadat; Pandey,Abhishek; Dasgupta,Rupa
Fonte: Rede Latino-Americana de Materiais Publicador: Rede Latino-Americana de Materiais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2015 EN
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Advantages of Cu based shape memory alloy include amongst other features, high transformation temperature, low cost of production, ease in manufacturing processes and ability to vary the achieved properties through alloying additions. It has been often reported that these alloys are very sensitive to the alloying additions in terms of properties achieved and phase precipitation necessary for development of shape memory properties. This behaviour in Cu based shape memory alloys i.e. being very sensitive to its constituents can be used positively to design alloys with pre set properties if the alloying additions and their percentages are properly controlled. In an attempt to understand the effect of different alloying additions, 2% of different elements [Zn, Si, Mg & Cr] were added to a known Cu-based shape memory alloy [Cu-12.5 wt% of Al-5 wt % of Mn]. The objective was to ascertain changes or improvements achieved due to the additions in terms of microstructural changes, hardness, phase precipitation and transformation temperatures. Attempts have been made to analyze the changes in properties achieved in the base Cu-Al-Mn alloys due to the quaternary additions. Grain structure with α+β phases, which is a pre requisite for martensite formation on quenching is seen in all the alloys indicating that all the alloys have potential to exhibit the shape memory behaviour. The martensite formation with different morphologies is observed in the quenched samples however. XRD results have identified the precipitated phases to be the martensitic phases. The DSC results indicate clear transformation peaks in most of the samples with significantly high transformation temperatures. The findings confirm the variation in properties achieved due to different additions and improvements achieved in terms of higher transformation temperatures and martensite formation due to the alloying additions. An attempt has been made to understand the findings.

Processing and properties of high performance 7075 Al and AZ91 Mg powder metallurgy alloys

Jabbari Taleghani, Mohammad Ali
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Tese de Doutorado
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Aluminum (Al) and magnesium (Mg) alloys have received considerable attention over the past decades as potential materials of choice to achieve significant weight savings. Although the market for Al and Mg products continues to grow, many opportunities remain untapped because of the low stiffness and strength of Al and Mg alloys in comparison with ferrous alloys and some other structural materials. On the other hand, grain refinement is considered an effective way to increase the strength of metallic materials. In recent years, high-energy milling has been widely exploited for the production of nanostructured materials, and grain sizes with nanometer dimensions have been observed in almost all high-energy milled pure metals, metallic alloys, and intermetallic compounds. Although the processing and characterization of nanostructured Al alloys and composites by mechanical alloying has been the subject of many studies, studies on the high-energy milling of Mg alloys are scarce. It should also be considered that to be suitable for structural applications, the nanocrystalline Al and Mg powders produced by mechanical alloying should then be consolidated to bulk materials. The consolidation route can have significant effects on the microstructure and mechanical properties of the processed bulk product. However...

MEAM potentials for Al, Si, Mg, Cu, and Fe alloys

Jelinek, Bohumir; Groh, Sebastien; Horstemeyer, Mark F.; Houze, Jeffery; Kim, Seong-Gon; Wagner, Gregory J.; Moitra, Amitava; Baskes, Michael I.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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A set of Modified Embedded Atom Method (MEAM) potentials for the interactions between Al, Si, Mg, Cu, and Fe was developed from a combination of each element's MEAM potential in order to study metal alloying. Previously published MEAM parameters of single elements have been improved for better agreement to the generalized stacking fault energy (GSFE) curves when compared with ab-initio generated GSFE curves. The MEAM parameters for element pairs were constructed based on the structural and elastic properties of element pairs in the NaCl reference structure garnered from ab-initio calculations, with adjustment to reproduce the ab-initio heat of formation of the most stable binary compounds. The new MEAM potentials were validated by comparing the formation energies of defects, equilibrium volumes, elastic moduli, and heat of formation for several binary compounds with ab-initio simulations and experiments. Single elements in their ground state crystal structure were subjected to heating to test the potentials at elevated temperatures. An Al potential was modified to avoid formation of an unphysical solid structure at high temperatures. The thermal expansion coefficient of a compound with the composition of AA 6061 alloy was evaluated and compared with experimental values. MEAM potential tests performed in this work...

Age hardening of the aluminium alloy EN 4017

Swanepoel,D.B.; Stumpf,W.E.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2009 EN
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Hulamin Rolled Products (Ltd) developed a high Mn and Si containing alloy, EN 4017 as a scrap consuming alloy from the waste generated in producing their range of clad products for brazing of inter alia automotive heat exchangers. The multifaceted composition of this alloy (Al -1.2 wt% Si -1.1 wt% Mn -0.2 wt% Mg -0.26 wt% Cu) suggested that it might display some degree of strengthening via precipitate formation of the Mg2Si-types. The aging isotherms constructed showed that EN 4017 with 0.19% Mg reached a lower peak strength (YS~210 MPa and UTS~260 MPa) compared to the EN 4017 material with 0.43% Mg (YS~270 MPa and UTS~325 MPa). The higher Mg variant of EN 4017 was comparable with the age-hardenable reference alloy EN 6061. Selected area electron diffraction (SAED) studies proved that the microstructure of age hardened EN 4017 contained a combination of B" and U2 phase after being aged at 175ºC for 65 h. The general microstructure contained precipitate free zones as well as grain boundary Si films, although these did not lead to significant embrittlement. The role of Mn dispersoids in the fracture mechanism of 4017 is also discussed. The article will compare the behaviour of EN 4017 with that EN 6061.