Improving microstructural properties, mechanical performance, and processability of flux-engineered stir cast boron carbide (B ₄ C)-reinforced AA6061 composites with K₂TiF₆ integration

Flux-assisted stir casting of AA6061–B₄C is limited by incomplete wetting, oxide films, and porosity. This study optimizes the K₂TiF₆-assisted process, defining a minimal effective flux window (0.5–1.0 wt%) while holding melt (≈750 °C), stirring (≈600 rpm, 10 min), and mold temperature (≈250 °C) constant and varying B₄C (4–12 wt%) in a single, industry-style rig. SEM/EDS/XRD indicate near-uniform dispersion to 10 wt% and mild clustering at 12 wt%. Measurable performance gains. Measured as group means ± SD (n = 3), microhardness (HV₀.₅) increased from 68 → 113 (+62%), and UTS rose from 142 → 215 MPa (+51.4%); porosity rose modestly (~1.5→3.5%). Rule-of-mixtures predictions reproduce the 4–12 wt% trend, supporting a mechanism in which low-dose K₂TiF₆ disrupts oxide films, enhances wetting, and improves load transfer. By quantifying a low-flux regime that limits Ti contamination and salt waste while delivering predictable structure–property outcomes, the work provides process-level guidance for scalable production of lightweight aluminum composites for weight-critical structural applications.