Corrosion Resistance of Cordierite-Modified Light MMCs

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JMEPEG (2017) 26:2555–2562 DOI: 10.1007/s11665-017-2706-7

Corrosion Resistance of Cordierite-Modified Light MMCs A. Szewczyk-Nykiel, P. Długosz, P. Darłak, and M. Hebda (Submitted November 12, 2016; in revised form April 17, 2017; published online May 2, 2017) Composites are one of the fastest developing materials. Research is particularly intensive in case of light metal alloys due to i.a. economic and environmental aspects. One of the innovative solutions is production of the metal matrix composites (MMC) by adding the cordierite ceramics obtained from fly ashes to magnesium alloys. In addition to obtaining new-generation materials with improved mechanical properties, also the waste is utilized which has a significant environmental and economic importance. In order to select the suitable operating conditions for such alloys, their corrosion resistance must be determined. This paper presents the results of corrosion resistance tests of AM60 magnesium alloy matrix composites reinforced with cordierite ceramics. The following issues were examined: (1) impact of the volume fraction of cordierite ceramics, 2 or 4 wt.%; (2) impact of surface roughness (two variants of surface treatment); and (3) impact of heat treatment on corrosion resistance of obtained composites. The results were compared with data recorded for the base AM60 alloy (which surface treatment was identical as of the composites). Moreover, the XRD and microanalysis of the chemical compositions by EDS method were applied to determine phases occurring in the investigated composites. Furthermore, the XRD was also performed in order to identify the corrosion products on the surface of the material. The test results indicate that the alloy reinforced with 2 wt.% addition of cordierite ceramics had the best corrosion resistance. It was also presented that surface and heat treatment affect the obtained results. Keywords

AM60 magnesium alloy, corrosion rates, electrochemical tests, metal matrix composites, surface roughness, squeeze casting, tafel slope

1. Introduction Light metal alloys are now increasingly used as structural materials. Among them, magnesium-based materials possess particular properties, having low density and high specific strength. They also have a unique capability of damping vibration. On top of that, they have low inertia and because of that they can be used for making parts which rapidly accelerate or decelerate. For these reasons, intensive research is focusing i.a. on manufacturing magnesium-based metal matrix composites (MMC). As a result of advancements in manufacturing technologies, these materials find application in many industries such as automotive and aerospace (Ref 1-3). One of the innovative solutions is production of the MMC by adding the cordierite ceramics obtained from fly ashes to magnesium alloys (Ref 4). In addition to obtaining newgeneration materials with improved mechanical properties, the waste is also utilized which has a significant environmental and economic importance. However, the mechanical strength of any mater