The Role of Barium in Structural Changes, Mechanical Properties, ‎and Wear Behavior of Al-20Mg2Si Composite

This study investigated the effect of adding barium elements with various weight percentages of 0.1, 0.2, 0.4, 0.6, 0.8, and 1% on different phases, mechanical properties, and wear resistance of the Al-20Mg2Si composite. The results showed that adding 0.2% barium modified the primary Mg2Si particles. However, with further increasing Ba content, this effect disappeared. The primary Mg2Si particles changed from coarse dendritic to small polygon. The average size decreased from 1178.5 to 289.1 μm, and the normalized area decreased from 1 to 0.7. The aspect ratio of the particles decreased from 1.2 to 1.1, and the number of particles increased from 9 to 41 mm2. The mechanism of barium modification can be heterogeneous nucleation on Al2Si2Ba particles and growth restriction. The eutectic Mg2Si structure also became fine flakes. The α-Al15Si2 (Fe, Mn) 3 emerged in addition to β-Al5FeSi after adding Ba. However, adding Ba did not cause any significant changes in the Al5Mg8Si6Cu2 and Al2Cu phases. Elastic Modulus, yield strength, ultimate tensile strength, elongation percentage, impact energy, and hardness increased by 22%, 24%, 30%, 20%, 33%, and 19% after adding 0.2% Ba, respectively. A large part of the fracture surface of the specimens was composed of cleavage plates, which indicated a brittle fracture mode consistent with a small elongation percentage. Modification decreased the wear rate from 1.9 to 1.2 mm3 / km, reduced the coefficient of friction from 0.58 to 0.54, and the weight loss from 7.1 to 4.8 mg for a sliding distance of 2000 m.