Manufacturing Technology Today

R. Kamal Jayaraj ¹, S. Malarvizhi ¹, V. Balasubramanian ²

Affiliations
1 Dept of Manufacturing Engineering, Annamalai University, Annamalai Nagar, Tamil Nadu, IN
2 Centre for Materials Joining and Research (CEMAJOR), Dept of Manufacturing Engineering, Annamalai University, Annamalai Nagar, Tamil Nadu, IN

Abstract

Joining of dissimilar alloys such as Aluminium (Al) and Magnesium (Mg) by fusion welding processes was very difficult due to formation of Al12Mg17 intermetallic compounds in fusion zone. However, friction stir welding (FSW) is expected to join dissimilar alloys with adequate joint strength because it is a solid-state process. But the Al/Mg FSW dissimilar joints are more prone to corrosion attack due to intercalated microstructure present in weld nugget (stir zone). The limitation of low corrosion resistance restricts practical applications of these types of joints. In this investigation, an attempt has been made to develop an empirical relationship to predict the corrosion rate of nugget region of friction stir welded dissimilar joints of AA6061 Al - AZ31B Mg alloys. Three important immersion corrosion test parameters, namely, chloride ion concentration, pH value and immersion time are chosen as input parameters. Three factors, five level, central composite rotatable design matrix is used to minimize the number of experimental conditions. Response surface methodology is used to develop an empirical relationship. The developed relationship can be effectively used to predict the corrosion rate of friction stir welded dissimilar joints of AA6061 Al - AZ31B Mg alloys at 95 % confidence level. The methodology adopted to develop the relationship is presented in this paper.

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R. Kamal Jayaraj ¹, S. Malarvizhi ¹, V. Balasubramanian ¹

Affiliations
1 Centre for Materials Joining and Research (CEMAJOR), Department of Manufacturing Engineering, Annamalai University, Annamalai Nagar, Tamil Nadu, IN

Abstract

Joining of magnesium alloys is increased because of its superior properties like light weight and high specific strength. Compared to fusion welding process, friction stir welding (FSW) is widely adaptable to join magnesium and its alloy. In the FSW joint, grains are very fine in stir zone (SZ) compared to the other zones. This leads to severe corrosion attack at the stir zone. The chloride ion concentration, pH value and immersion time are reported to be the more influencing parameters on corrosion attack. The present work aims to identify the minimum corrosion conditions in the SZ of friction stir welded AZ31B magnesium alloys by statistical tools such as design of experiments (DoE), analysis of variance and response surface methodology (RSM). From the results, it is found that the chloride ion concentration has a greater influence on corrosion rate than the other two parameters.

Keywords

Friction Stir Welding, AZ31B Magnesium Alloy, Response Surface Methodology, Corrosion Rate.

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