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ORIGINAL ARTICLE

Microstructural and Wear Investigations of the Mg/B4C Surface Composite Prepared Through Friction Stir Processing Sumit Joshi1

•

N. Yuvaraj1 • Ramesh Chandra Singh1 • Rajiv Chaudhary1

Received: 9 June 2020 / Accepted: 4 October 2020 Ó The Indian Institute of Metals - IIM 2020

Abstract Friction stir processing (FSP) is one of the potential fabrication methods that usually modify the microstructural and wear characteristics of the material in the form of surface composite, thus enhancing the surface characteristics, namely hardness and wear resistance. In the present study, B4C particles were reinforced in the as-cast magnesium alloy (Mg–4Al–3Zn–3Sn–3Pb) matrix surface using FSP to produce the surface composite. The subsequent investigation signified the role of B4C particles on the microstructural and wear attributes of the magnesium alloy. The microstructural features revealed very fine grain structure and homogeneous dispersion of B4C particles in the surface composite produced. The reinforcement of hard and brittle B4C improved the hardness and wear properties of as-cast magnesium alloy. The predominant wear mechanisms identified in as-cast specimens were adhesion and abrasion, which transformed to abrasion and delamination with the addition of B4C particles. Keywords B4C  Friction stir processing  FSP  Magnesium alloy  Surface composite  Wear

& Sumit Joshi [email protected] N. Yuvaraj [email protected] Ramesh Chandra Singh [email protected] Rajiv Chaudhary [email protected] 1

Department of Mechanical Engineering, Delhi Technological University, Bawana Road, New Delhi 110042, India

1 Introduction In the present scenario, there has been a sharp rise in the usage of lightweight components, especially in the aircraft and automotive applications. Magnesium alloys are among the lightweight materials that offer properties such as high specific strength, excellent machinability, better damping capacity and recycling potential. Magnesium is the lightest among all structural metals having unit weight of approximately two-third of its counterpart aluminium and onethird of steel. The outstanding strength–weight ratio property of magnesium gives them a major advantage in industrial applications since light-weight results in the reduction in fuel consumption as well as greenhouse gas emissions [1–4]. In applications where there is relative motion between the components, the service life is greatly influenced by its surface characteristics rather than bulk. A good surface behaviour is desired for an element to have excellent mechanical and tribological features at the surface [5, 6]. It can be achieved by employing surface modification techniques either in a liquid state or in a solid state. Liquid-state techniques such as coating and spraying methods, laser melt treatment and plasma spraying involve melting of the matrix during processing, which results in interfacial reaction and low surface finish. Moreover, these techniques undergo liquid or semi-solid phase while fabrication, which r