• PDF / 2,726,014 Bytes
• 11 Pages / 595.276 x 790.866 pts Page_size
• 67 Downloads / 250 Views

DOWNLOAD

REPORT

---

Microstructure and Mechanical Properties of AM60 Magnesium Alloy Processed by a New Severe Plastic Deformation Technique Siroos Ahmadi1 · Ghader Faraji2 · Vali Alimirzaloo1   · Ali Donyavi3 Received: 23 July 2020 / Accepted: 24 September 2020 © The Korean Institute of Metals and Materials 2020

Abstract  The mechanical properties and microstructure of AM60 Magnesium alloy processed by a new cyclic extrusion channel angular pressing (CECAP) technique were investigated in this research. In this novel method, a low extrusion ratio stage was added at the end of the CECAP process to enhance the hydrostatic stresses and equivalent strain. The structure was refined from the average grain size of ~ 76 µm for the annealed samples to 2.63 µm in the new CECAP after four passes. While for the CECAP and ECAP processes, it was 3.43 and 6.98 µm, respectively. Experimental results of the proposed CECAP process showed an improvement in the mechanical properties after the second pass that were stopped for the ECAP process. However, the hardness of the CECAP-processed and proposed samples was constantly increasing. This increase in hardness was 196% and 175% for the proposed CECAP and CECAP processes after four passes compared to the unprocessed sample, respectively. Moreover, the compressive yield stress and ultimate compressive strength of the CECAP-processed samples were higher in all passes; however, they were smaller than those of the proposed CECAP process. The hydrostatic compressive stresses and higher plastic strain in the proposed technique helped in further refining of the grains, which can effectively improve the mechanical properties. Keywords  Novel CECAP process · AM60 alloy · Grain refinement · Mechanical properties · Microstructure

1 Introduction Magnesium (Mg) and its alloys have several interesting properties, including high strength to weight ratio, good recyclability, and resistance to heat changes as well as biocompatibility and corrosion resistance in body fluids [1–3]. However, their low plasticity especially at ambient temperature [due to their compressed hexagonal close-packed (HCP) crystal structure] and low slip system have restricted their applications [4]. Considering the HCP structure and ductility restrictions, Mg alloys have been often fabricated through casting instead of plastic deformation. Hence, to enhance the applicability of this alloy in the automotive and * Vali Alimirzaloo [email protected] 1



Department of Mechanical Engineering, College of Engineering, Urmia University, Urmia 57153165, Iran

2



School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran 11155‑4563, Iran

3

Department of Industrial Engineering, College of Engineering, Urmia University, Urmia 57153165, Iran



aerospace industries, their workability and strength should be improved. The microstructure refinement by severe plastic deformation (SPD) techniques can enhance the biocompatibility and mechanical properties for the medical applications [5–8]. The improvement in the mechanic