Effect of artificial ageing treatment and precipitation on mechanical properties and fracture mechanism of friction stir processed MgZn2 and Al3Sc phases in aluminium alloy. (2021)

• Record Type: Journal Article
• Authors: Mandal, P.K.; John Felix Kumar, R.; Merrin Varkey, J.
• Is Part Of: Materials today. Volume 46:Part 10(2021)
• Page Start: 4982
• Page End: 4987
• Publication Date: 2021
• Subjects: Nanoparticles-Al3Sc -- TEM -- DP-FSP -- SEM fractography -- Strength; Materials science -- Congresses -- Periodicals; 620.1
• DOI: 10.1016/j.matpr.2020.10.389
• Languages: English
• ISSNs: 2214-7853

Abstract

Abstract: Aluminium alloy (7075 series) contains scandium (Sc) promoting fine grains due to their potent inoculation effects formation of homogeneous primary particles, Al3 Sc (L12 ) during solidification and subsequent age- hardening phenomenon. A supersaturated aluminium matrix can ensure the driving force for the coherent precipitates, and high density (∼0.45 wt% Sc) nanoparticles Al3 Sc and further enhanced by raising the ageing temperature. FSP is a solid-state surface modification technique via frictional heat and tool stirring during processing. The effects of double-pass friction stir processing (DP-FSP) on the microstructure, and nano-sized particle (MgZn2, Al3 Sc) distribution, as well as the microstructural evolution after T6 heat treatment, were investigated by OM, FESEM, TEM, SEM, Vicker's hardness measurement, and tensile properties. Zn vaporization is a primary defect in the stirring zone which hinders the high strength even though having fine grain microstructures. SEM fractography revealed coarse precipitates, defects, and propagation of fracture plane of the alloy. The present investigation aims to study the enhancement of strength and ductility for nano-sized precipitates in the matrix by a combination of T4 + DP-FSP and subsequent post ageing treatment at 140 °C for 2 h (T6 treatment).