Assessment of surface hardness and tribological behavior of friction stir processed Mg-3Zn squeeze casted alloy for lightweight applications Bewertung der Oberflächenhärte und des tribologischen Verhaltens einer durch Reibrühren bearbeiteten Mg-3Zn-Squeeze-Cast-Legierung für Leichtbauanwendungen

Abstract

Magnesium alloys are promising candidates for lightweight structural applications; however, their limited hardness and wear resistance restrict wider use, particularly in power train and transmission system components. In this study, friction stir processing (FSP) was employed to improve the surface properties of squeeze-casted Mg–3Zn alloy. Optical microstructural analysis revealed significant grain refinement in the processed zone, with the average grain size reduced from 55 μm to 6 μm due to dynamic recrystallization. The refined equiaxed grains and increased high-angle grain boundary density contributed to grain-boundary strengthening, consistent with the Hall–Petch mechanism, resulting in a 76 % increase in surface microhardness (67 HV to 118 HV). Tribological evaluation under applied loads of 15 N–45 N demonstrated superior wear resistance of the friction stir processed alloy, with a 48.5 % reduction in wear loss at 15 N and lower coefficients of friction compared to the as-cast alloy. Worn surface analysis indicated abrasion and oxidation at lower loads, while delamination dominated at higher loads. The enhanced tribological performance confirms the suitability of friction stir processed Mg–3Zn alloy for lightweight power train and transmission applications.