Microstructural modification of cast Mg alloys by friction stir processing

Abstract

Cast Mg alloys were processed using friction stir processing (FSP) to acquire a fine grained structure and high strength. Actually, FSP is a novel grain refinement method for light metal alloys. Using FSP, a cast microstructure with coarse grain size was refined to equiaxial fine grain through dynamic recrystallisation; second phase particles were finely dispersed by FSP. Moreover, FSP is effective to eliminate cast defects such as microshrinkages or porosities. Commercial die cast Mg alloy (AZ91D) and high strength Mg-Y-Zn alloy plates were prepared for FSP. Heat input using a rotational tool during FSP closely affected the microstructure in the stirred zone. Actually, FSP with lower heat input produced a finer grain size and higher hardness. Changes in the friction stir processed microstructures affecting mechanical properties were not only grain refinement, but also second phase particle distributions. Results show that alloys with high hardness by FSP have finely dispersed second phase particles without dissolution during FSP.

Fabrication of a novel hydroxyapatite/polyether ether ketone surface nanocomposite via friction stir processing for orthopedic and dental applications

“…FSP method has been widely used for fabricating substrates made of magnesium (Morishige et al 2008) and titanium (Farnoush et al 2013b). Although some thermoplastic polymers have been treated using this method (Gan et al 2010;Prasad and Raghava 2012), some concerns relating to macromolecular chain breaking are raised as a result of tool pin rotation (Gan et al 2010).…”

The microstructure and wear behaviour of friction stir processed AISI 430 ferritic stainless steel

“…Many attempts have been made to develop new tool materials and tool designs for the FSP of hard alloys [16]. FSP is advantageous in microstructural modifications including homogenization of surface phases [17], surface composites [18] and microstructural refinement [19].…”

Critical Assessment 25: Friction stir processing, potential and problems

“…The earliest application of FSP involved evaluating the potential for grain refinement of alloys, and this has continued to be a key focus, with studies involving cast Al, Mg, and Ti alloys [7,8], with methods for producing ultrafine ( < 1 μm) [9] or even nanograined structures in Mg alloys feasible [10], with compositions summarised in Table 1. The external cooling or quenching applied during FSP suppresses grain growth during the cooling period on the trailing edge of the tool.…”