Effect of tool tilt angles on the formation of YSZ/Al₂O₃ hybrid surface composites on friction stir processed magnesium alloy AZ31

Abstract Friction stir processing (FSP) is a well-known method for improving metal alloys’ surfaces by producing surface composites with better mechanical properties. This study examines how the tool tilt angle affects the FSP region generation in an AZ31 magnesium (Mg) alloy reinforced with yttria-stabilized zirconia (YSZ) and alumina (Al 2 O 3 ). The effect of different tool tilt angles (T TA ) on the dispersion, integration, and distribution of YSZ and Al 2 O 3 in the Mg matrix was investigated. Optical microscopy, scanning electron microscopy (SEM), and Vickers hardness testing were used to extensively evaluate the microstructural and mechanical characteristics of the FSP-treated region. The findings show that the T TA has a major impact on the surface composite’s homogeneity and uniformity, with 2° T TA encouraging the best possible dispersion of YSZ/Al 2 O 3 and enhanced mechanical properties. T TA of 2° friction stirred surface hybrid composite (FSSHC) exhibits a greater hardness of 137 HV as compared to the FSP-treated (106 HV) and the base alloy (73 HV). This is due to the Orowan strengthening mechanism and also because FSSHC has the ability to withstand a load through the inclusion of YSZ/Al 2 O 3 particles, and the homogeneous distribution of YSZ/Al 2 O 3 particles among the recrystallized base alloy grains provides homogeneous reinforcement across the stirred region.