Influence of heat treatment on corrosion resistance of pm composite materials based on en AW-2124 aluminum alloy reinforced with the Al2O3 ceramic particles
Leszek A. Dobrzański*, Anna Włodarczyk*, Marcin Adamiak*, Ginter Nawrat** *Politechnika Śląska, Wydział Mechaniczny Technologiczny, Instytut Materiałów Inżynierskich i Biomedycznych, ul. Konarskiego 18a, 44-100 Gliwice **Politechnika Śląska, Katedra Chemii i Technologii Nieorganicznej, ul. Krzywoustego 6, 44-100 Gliwice
Quarterly No. 1, 2005 pages 30-34
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abstract Investigation results are presented of the heat treatment effect on the corrosion resistance of the aluminium-ceramic particles composites. Examinations were made of the EN AW-2124 aluminium alloy (Table 1), and also of the composite materials with the matrix from this aluminium alloy reinforced with the Al2O3 ceramic particles with varying volume fractions. The Xray phase analysis of the composite materials made it possible to identify reflections coming from the aluminium matrix and of the reinforcing particles (Fig. 1). The metallographic examinations of the investigated composite materials made it possible to observe the homogeneous distribution of the reinforcing material in the matrix; however, banding of the reinforcing particles parallel to the extrusion direction was noted on the longitudinal microsections (Fig. 2). Examinations of the composite materials on the scanning electron microscope before their heat treatment made it possible to reveal occurrences of the Al-Cu-Mg-Mn intermetallic phases precipitations (Fig. 3). The investigated materials were subjected to heat treatment to improve their corrosion resistance. The same types of the composite materials were also examined without the heat treatment, which made it possible to compare their corrosion resistance in both states. The analysed results of the corrosion tests, determined using the potentiodynamic method in the 3% water solution of NaCl indicate that the corrosion susceptibility of the investigated composite materials depends on the volume fraction of the reinforcing particles and also on the state in which they were examined. It was found out, basing on the determined anode polarisation curves and also on the electrochemical parameters (Table 2) that the investigated materials are susceptible to pitting corrosion. The investigation results indicate that the composite materials reinforced with the ceramic particles with the portions of 5 and 10% are characteristic of a higher corrosion resistance in the selected environment, compared to the matrix material, whereas at the 15% portion this resistance is worse, the anode digestion current grows and the anode polarisation resistance decreases. Comparison of the corrosion test results in both states makes it possible to state that the heat treatment improves the corrosion resistance of the composite materials. The exemplary microphotographs of the examined specimens’ surfaces after the corrosion tests (Fig. 5) confirm the analysed investigation results. Key words: aluminum alloy, composite materials, powder metallurgy, corrosion resistance, polarisation curve