Influence of rotational speed on the microstructural, mechanical and wear behaviour of FSPed cast AZ91 magnesium alloy

ABSTRACT

In this study, the Magnesium AZ91 alloy underwent a process known as Friction Stir Processing (FSP) at different tool rotational speeds: 1160 r.p.m., 850 r.p.m., and 580 r.p.m. subjected to a constant transverse speed/feed rate (50 mm/min). The average grain size of the FSP-processed samples fell dramatically due to dynamic recrystallisation (DRX), from 43.65 μm in the as-received Mg AZ91 to less than 4.21 μm in the alloy processed at 850 rotational speed. The UTS was enhanced from 145.49 MPa to 184.51 MPa for as-received material to alloy processed at 850 rotational speeds due to the dissolution of secondary phases and the grain refinement. Also, this increase in rotational speed resulted in an increase in total elongation (TE), which increased from 5.465% to 9.92% due to the removal of defects during the processing. The wear resistance of FSPed materials was better than that of the as-received material at all tool rotational speeds. Better wear resistance was observed in the case of samples processed at 850 r.p.m. All these alterations in properties were found due to the existence of refined grains and the removal of defects due to stirring action.

KEYWORDS:

• AZ91 magnesium alloy
• grain refinement
• FS processing
• tensile strength
• wear resistance

Disclosure statement

No potential conflict of interest was reported by the author(s).