Investigating effects of process parameters on microstructural and mechanical properties of Al5052/SiC metal matrix composite fabricated via friction stir processing A. Dolatkhah ⇑ , P. Golbabaei, M.K. Besharati Givi, F. Molaiekiya School of Mechanical Engineering, University College of Engineering, University of Tehran, Tehran, Iran article info Article history: Received 9 July 2011 Accepted 15 September 2011 Available online 22 September 2011 Keywords: A. Metal matrix composites E. Mechanical F. Microstructure abstract Friction stir processing (FSP) is a novel process for refinement of microstructure, improvement of mate- rial’s mechanical properties and production of surface layer composites. In this investigation via friction stir processing, metal matrix composite (MMC) was fabricated on surface of 5052 aluminum sheets by means of 5 lm and 50 nm SiC particles. Influence of tool rotational speed, traverse speed, number of FSP passes, shift of rotational direction between passes and particle size was studied on distribution of SiC particles in metal matrix, microstructure, microhardness and wear properties of specimens. Optimum of tool rotational and traverse speed for achieving desired powder dispersion in MMC was found. Results show that change of tool rotational direction between FSP passes, increase in number of passes and decrease of SiC particles size enhance hardness and wear properties. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Increase of aluminum alloys application in industry and debility of fusion welding in creation of reliable joints for these alloys, led to development of friction stir welding (FSW) as a novel solid state welding method [1]. In this method a non-consumable rotating tool with special geometry consisting of a pin and a shoulder en- ters the weld seam and joins the workpieces with traversing along the seam. FSW is capable of joining materials which can be hardly joined with common fusion welding techniques [2]. For instance Cavaliere et al. [3] utilized FSW for creating dissimilar 2024– 7075 aluminum alloy joints. Along with development of this solid state welding method, FSP was invented based on FSW [4]. In fric- tion stir processing instead of welding two different pieces, tool will be inserted into a single part. Tool shoulder plays a key role in generation of surface friction and rise of workpiece temperature. Tool pin generates stirring and therefore materials in processed zone experience sever plastic deformation. Flowing and recrystal- lization in processed zone occurs with tool rotation and linear movement. This results in creation of a fine equiaxed microstruc- ture. Refinement and modification of microstructure leads to sig- nificant improvement of mechanical properties in stirred zone. El-Danaf et al. [5] reported that during FSP the ductility of the fric- tion stir processed 5083Al was enhanced by a factor ranging from 2.6 to 5 compared to the ductility of the as-received material, in the range of the strain rates tested. Also superplasticity enhance- ment [6] and increase of material formability and toughness [7] were achieved via FSP of aluminum alloys. Fig. 1 shows FSP layout. FSP can be employed for production of metal matrix composites (MMCs) [8]. MMCs have magnificent surface properties such as high hardness value and noticeable wear resistance despite that they show poor tensile behavior and impact strength. With fabrica- tion of a MMC layer on surface of a metal sheet we can simulta- neously benefit considerable surface properties of MMC and proper tensile properties of bulk material. Various methods are available for production of MMC layers [9,10] nevertheless FSP is a simple and convenient way among them. 5052 aluminum as an Al–Mg series alloy has great appliance in military and marine industries. This alloy is non-heat-treatable, has high corrosion resistance, significant tensile strength and suit- able formability. Surface properties of this alloy can be improved with fabrication of a metal matrix composite layer on its surface. Some investigations have studied formation of MMCs by means of FSP method. For instance formation of AZ31/SiC composite layer [11] and Al–Mg/SiC composite layer [12] was reported. Hence there are no detailed references for selecting optimum process parameters to produce an Al5052/SiC MMC layer with desired properties. In the present study, capability of FSP in modifying Al5052 sur- face properties and formation of Al5052/SiC composite was inves- tigated for the first time. Effect of tool rotational and traverse speed 0261-3069/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2011.09.035 ⇑ Corresponding author. Address: School of Mechanical Engineering, College of Engineering, University of Tehran, Kargar Shomali St., P.O. Box: 11155/4563, Tehran, Iran. Tel.: +98 9125123015; fax: +98 2188013029. E-mail addresses: dolatkhah.a@gmail.com, a.dolatkhah@ut.ac.ir (A. Dolatkhah). Materials and Design 37 (2012) 458–464 Contents lists available at SciVerse ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes