Volume 9 Issue 1
Anodization Mechanism on SiC Nanoparticle Reinforced Al Matrix Composites Produced by Power Metallurgy
Sonia C. Ferreira, Ana Conde, María A. Arenas, Luis A. Rocha and Alexandre Velhinho
1Materials Research Centre/Institute for Nanostructures, Nanomodelling and Nanofabrication (CENIMAT/I3N), Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
2Centro Nacional de Investigaciones Metalúrgicas (CENIM-CSIC), Avda. Gregorio del Amo, 8, 28040 Madrid, Spain
3Centre for Mechanics and Materials Technologies (CT2M), Research Group on Functionalized Materials and Surfaces Performance, Campus de Azurém, 4810-058 Guimarães, Portugal
4Departamento de Física, Faculdade de Ciências, Campus de Bauru, Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP), Av. Eng. Luiz Edmundo Carrijo Coube, 14-01, 17033-360 Bauru, SP, Brazil
5Departamento de Ciência dos Materiais (DCM), Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal
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Abstract
Specimens of aluminum-based composites reinforced by silicon carbide nanoparticles (Al/SiCnp) produced by powder metallurgy (PM) were anodized under voltage control in tartaric-sulfuric acid (TSA). In this work, the influence of the amount of SiCnp on the film growth during anodizing was investigated. The current density versus time response and the morphology of the porous alumina film formed at the composite surface are compared to those concerning a commercial aluminum alloy (AA1050) anodized under the same conditions. The processing method of the aluminum alloys influences the efficiency of the anodizing process, leading to a lower thicknesses for the unreinforced Al-PM alloy regarding the AA1050. The current density versus time response is strongly dependent on the amount of SiCnp. The current peaks and the steady-state current density recorded at each voltage step increases with the SiCnp volume fraction due to the oxidation of the SiCnp. The formation mechanism of the anodic film on Al/SiCnp composites is different from that occurring in AA1050, partly due the heterogeneous distribution of the reinforcement particles in the metallic matrix, but also to the entrapment of SiCnp in the anodic film.
Keywords:aluminum matrix composite; powder metallurgy; anodizing; oxide film; nanosized reinforcements