Microstructure, mechanical properties, and wear resistance of friction stir back extruded brass-Ti2SnC composite

This study investigates the microstructure, mechanical properties, and wear behavior of Brass–Ti₂SnC composites fabricated by friction stir back extrusion (FSBE). Composites containing 0 vol%, 3 vol%, and 6 vol% Ti₂SnC were examined. The average grain size was 4.3 μm for 0 vol%, increased to 8.7 μm for 3 vol% due to reduced strain during processing, and decreased to 4.8 μm for 6 vol% as the higher reinforcement content enhanced grain boundary pinning. Electron backscatter diffraction (EBSD) confirmed that all samples exhibited discontinuous dynamic recrystallization (dDRX), with twin formation decreasing from 0 vol% to 6 vol% due to lower deformation levels. Pole figure intensities declined from 2.8 (0 vol%) to 1.7 (3 vol%) and 1.4 (6 vol%), indicating weaker texture development with increasing Ti₂SnC content. Mechanical testing showed that the yield strength increased from 105.2 ± 9.1 MPa (0 vol%) to 320.4 ± 8.1 MPa (3 vol%) and 356.7 ± 10.2 MPa (6 vol%), while the ultimate tensile strength rose from 300.4 ± 9.4 MPa to 572.1 ± 9.5 MPa for the 6 vol% composite. Hardness also improved significantly, from 110.2 ± 9.8 HV to 280.5 ± 53.2 HV as the Ti₂SnC content increased from 0 to 6 vol%. At 250 °C, the wear rate decreased from 5.2 µg/m (0 vol%) to 4.3 µg/m (6 vol%), and the friction coefficient dropped from 0.43 to 0.33. At 400 °C, the wear rate for the 6 vol% composite remained lower (4.9 µg/m) than that of the unreinforced brass (5.8 µg/m). Furthermore, the reinforced composites developed a thicker mechanically mixed layer (MML), which acted as a protective barrier and enhanced wear resistance.