Optimizing Surface Quality of TiO2/Ag Reinforced Magnesium Composites Using RSM-based Desirability–Function Analysis Fabricated by FSP Process

Abstract

Magnesium alloys are utilized in the aerospace, marine, and medical industries because of their low density and favourable mechanical properties. However, their hexagonal close-packed (HCP) crystal structure results in poor wear resistance and formability, which limits their large-scale applications. Enhancing the surface quality is an effective strategy to overcome these limitations. Friction Stir Processing (FSP) has emerged as a promising technique for microstructural refinement and surface modification. In this study, a novel hybrid surface composite of AZ91D reinforced with TiO₂ and silver nanoparticles (AgNPs) was fabricated using FSP. The experimental design was carried out using a Box–Behnken Design (BBD) based on Response Surface Methodology (RSM). Multi-objective optimization was performed using desirability function analysis (DFA) to achieve enhanced surface characteristics. The optimal process parameters were identified as a tool rotation speed (TRS) of 900 rpm, tool traverse speed (TTS) of 70 mm/min, number of passes (NoP) of 4, and reinforcement fraction (Rf) of 2 wt.%. Under these conditions, the microhardness of the composite increased by ~ 200% (from 60 to 70 Hv for the base material to 141.41 Hv).also wear rate was decreased by ~ 42% (from 5.6 × 10⁻³ to 3.26 × 10⁻³ mg/m). Scanning Electron Microscopy (SEM) analysis of the worn surfaces was conducted to investigate the prevailing wear mechanisms.