Taguchi Optimisation of Friction Stir Processing Parameters to Achieve Maximum Tensile Strength of Mg AZ31B Alloy
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TECHNICAL PAPER
TP 2580
Taguchi Optimisation of Friction Stir Processing Parameters to Achieve Maximum Tensile Strength of Mg AZ31B Alloy G. Venkateswarlu • M. J. Davidson G. R. N. Tagore
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Received: 19 April 2012 / Accepted: 24 July 2012 / Published online: 30 August 2012 Ó Indian Institute of Metals 2012
Abstract In this investigation, the effect of friction stir processing process variables such as rotational speed, traverse speed and tool tilt angle on the tensile strength of magnesium alloy AZ31B was studied. The experiments were carried out according to the Taguchi parametric design L9 at various combinations of process parameters and statistical optimization technique ANOVA was used to determine the optimum levels and to find the percentage of contribution of the process parameters. The results indicate that the rotational speed is the most significant factor followed by the traverse speed and tool tilt angle for maximising the tensile strength of the friction stir processed magnesium alloy. Keywords Taguchi Friction stir processing Magnesium alloy ANOVA
1 Introduction Magnesium alloys have been widely used for structural components in automotive, aerospace and electronic industries due to its favourable characteristics of light weight, high specific stiffness, high specific strength, and so on [1]. However, Mg alloys exhibit poor ductility because of hexagonal closed packed structure (hcp). Many researchers found that the properties of Mg alloys can be improved through refinement of grains [2–4]. Dynamic recovery induced by plastic compatibility stress and activation of non
G. Venkateswarlu (&) M. J. Davidson G. R. N. Tagore Department of Mechanical Engineering, NIT, Warangal 506004, A.P, India e-mail: [email protected]
basal dislocation slip systems improve ductility [5]. The results also indicated that improved mechanical properties can be attained by refining and homogenising the grain structure of the sheet. Recently, friction stir processing (FSP) has been developed to be an effective and efficient new method for the microstructural modification [6, 7]. FSP produces equiaxed homogeneous microstructure with fine grains by providing intense plastic deformation as well as higher strain rates than other methods [8–10], resulting in enhancement of mechanical properties. Friction stir processing has been successfully applied to many aluminium alloys for improving mechanical properties [11–14]. An extensive literature review revealed that only limited work has been carried out on the FSP of magnesium alloys. Darras et al. [15] studied the effect of various FSP parameters on the thermal histories and properties of commercial AZ31B-H24 magnesium alloy sheet. They found that grain refinement and homogenisation of microstructure can be achieved in a single pass through severe plastic deformation. The properties can be controlled by varying heat input during processing [16, 17]. In FSP, the tool rotational speed results in stirring and mixing of the material around the rotating pin which in
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