Study on surface modification and fabrication of surface composites of magnesium alloys by friction stir processing: a review

Abstract

AbstractMagnesium alloys and their composites are fast replacing aluminum alloys and other materials in the aerospace and automotive industries. Significant progress has been made in the fabrication of these composites to make them materials of choice for these industries. The choice of the fabrication process is crucial to realize the composites with properties that can compete with the materials currently in vogue. Conventional methods of fabrication of magnesium alloys and their composites are seriously limited as they lead to defects such as porosity and particle clustering. Friction stir processing (FSP) is turning out to be a promising fabrication technique to surmount these challenges. The process being a solid state technique is highly amenable to production of surface modified composites with very attractive mechanical and tribological properties. The main factor making FSP attractive is the relative ease of modification of the surface layers and the incorporation of reinforcement particles. The underlying plastic deformation in FSP ensures that the reinforcement particles are incorporated and distributed uniformly throughout the matrix. This paper attempts to review the current status of FSP as a technique of enabling the surface modification and fabrication of surface composites of magnesium alloys. The objective is to summarize the progress made towards the realization of surface-modified magnesium alloys, primarily in two systems, namely, Mg-AZ system and Mg/rare earth system. The operating conditions (and process parameters) and their subsequent effect on mechanical and tribological properties of the fabricated composites are summarized through the consideration of fabrication of three representative systems, viz., Mg-metal oxide (Mg-MO), Mg-metal carbide (Mg-MC), and Mg-carbon nano tube (Mg-CNT) systems.