Corrosion-wear behavior of AA1050/mischmetal oxides surface nanocomposite fabricated by friction stir processing Mahdi Alishavandi a , Mohammad Amin Razmjoo Khollari a , Mahnam Ebadi b , Sajjad Alishavandi c , Amir Hossein Kokabi a, * a Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 1365-9466, Azadi Avenue,14588, Tehran, Iran b Department of Materials Science and Engineering, Shiraz University, P.O. Box 71557-13876, School of Engineering, Zand Boulevard Shiraz, Iran c Department of Mechanical Engineering, Islamic Azad University Shiraz Brach, P.O. Box 74731-71987, Shiraz, Iran article info Article history: Received 23 October 2019 Received in revised form 7 January 2020 Accepted 20 January 2020 Available online 21 January 2020 Keywords: AA1050 Friction stir processing Mischmetal oxide Nanocomposite Wear Corrosion abstract In this study, the wear and corrosion characteristics of six-pass friction stir processed (FSPed) AA1050/ mischmetal oxide nanocomposite (6PPA) was compared to six-pass FSPed sample without powder (6 PA) and annealed base metal (BM). Different wear characteristics, such as weight loss, wear rate and coef- ficient of friction (COF) were studied. In order to evaluate the corrosion resistance of samples, immersion and cyclic polarization tests were performed. In addition, worn and corroded surfaces were investigated by field emission scanning electron microscopy (FESEM). The result of pin on disk dry sliding wear test revealed that wear resistance improved by employing FSP through finer grain structure (6 PA sample) and by incorporation of mischmetal oxides (MMOs) through lubrication and load-bearing action of particles (6PPA sample). At the constant load of 30 N, COF decreased from 0.9 to 0.85 and 0.75, and weight loss from 7.4 to 5.7 and 4.5 mg/m  10 3 for the BM, 6 PA, and 6PPA samples, respectively. According to FESEM study of the worn surfaces, the BM and 6 PA samples show an adhesive wear mechanism, however the wear mechanism changed to abrasive for 6PPA sample. Based on immersion test results, corrosion rate of BM reduced from 0.41 to 0.36 and 0.29 mpy for the 6 PA and 6PPA samples, respectively. Moreover, the results of cyclic polarization test and FESEM investigation showed improved pitting resistance of 6PPA sample. © 2020 Published by Elsevier B.V. 1. Introduction Aluminum metal matrix composites (AMMCs) supply ~70% of metal matrix composite of industries. Global demand for AMMCs in various industries such as aerospace, automotive, and electronics equipment has been raised as a result of high specific strength, low specific weight, good formability and excellent corrosion resistance [1e3]. Aluminum metal matrix nanocomposites (AMMNCs) are the cutting edge of the aluminum industry since they exhibit unique mechanical properties and compensate for the disadvantages of aluminum such as softness and low wear resistance [4]. An outstanding wear performance can be achieved by incorporation of ceramic reinforcing particles into the Aluminum matrix, using FSP. The main advantage of this method is maintaining the crude properties of bulk. Formation of thoroughly homogenized and ultra-fine grained (UFGed) microstructure containing high angle grain boundaries, beside the strengthening effect of reinforcing particles are the main reasons for improvement of mechanical properties [4e6]. Various researches studied the wear and corrosion resistance of FSPed AMMCs. Ravindranath et al. [7] investigated the wear behavior of hybrid AMMC reinforced with boron carbide and graphite particles. The composite showed better wear resistance owing to reinforcing effect of particles which provides an excellent resistance to micro-cutting. Mehta et al. [8] assessed wear prop- erties of the aluminum composite produced by FSP and reinforced with boron carbide. Pin-on-disc wear test showed 75% less wear rate for FSPed AMMCs in comparison with AA6061-T6. They contributed the improved properties to the grain structure refine- ment and homogenous particles distribution through BM. Zhang * Corresponding author. E-mail addresses: Mahdi.alishavandi2015@student.sharif.edu (M. Alishavandi), M.razmjoo94@student.sharif.edu (M.A. Razmjoo Khollari), Ebadi.mahnam@gmail. com (M. Ebadi), Sajjad_alishavandi@icloud.com (S. Alishavandi), kokabi@sharif. edu (A.H. Kokabi). Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom https://doi.org/10.1016/j.jallcom.2020.153964 0925-8388/© 2020 Published by Elsevier B.V. Journal of Alloys and Compounds 832 (2020) 153964