The paper studies the application of mechanical alloying technology for producing Al-Pb composites with improved mechanical and antifriction properties. The technology is shown to be highly efficient. Mechanical alloying of aluminum with lead increases the hardness, strength, and wear resistance of materials almost twofold and ensures excellent high-temperature strength owing to the formation of a fine-crystalline base structure (grains smaller than 1 μm) with lead particles (no more than 2 μm).Antifriction Al-based sintered materials have low density, low cost, high corrosion resistance, good antifriction properties, and are substitutes of tin bronze [1]. Materials based on Al-Pb hold much promise as a base [2][3][4][5]. However, their great disadvantage is low strength, which substantially reduces ultimate loads. The best mechanical properties are offered by the materials based on a granulated Al-Pb composite produced by melt dispersion in water [5]. Unfortunately, the material containing 10% Pb has low strength either, no more than 150 MPa. The mechanical and antifriction properties can be substantially improved by applying the reactive mechanical alloying technology to ensure dispersion hardening of the base [6][7][8].This study is focused on the potential application of the mechanical alloying technology to produce nanocrystalline dispersion-hardened antifriction Al-Pb composites with excellent mechanical and antifriction properties.
RESEARCH TECHNIQUE, MATERIALS, AND EQUIPMENTThe main starting materials were: powders of aluminum (PA4), lead, and metal oxides: CuO, Co grade) with particles of 63 to 125 µm. Lead amounted to 5, 10, and 15 wt.% and alloying oxides to 5 wt.% in the composites. A composite containing 10% Pb was used for basic research. Higher fatty acid (HFA) C 17 H 35 COOH was introduced as a surface-active agent into all composites.The materials were mechanically alloyed in a vibration mill (mechanical reactor) at an energy density of 0.18 J ⋅ g -1 reached when the process chamber was 75% filled with steel balls (11.15 mm in diameter), the charge ratio was 8, and normal acceleration of the balls was 120 m ⋅ sec -2 . The Al-Pb-oxide composites were mechanically alloyed in two stages: (i) grinding a mixture of aluminum and alloying oxides for 6 h and (ii) treating the Pb-containing mixture for no less than 2 h. Particles of the granulated material varied from 0.4 to 0.8 mm. The Al-Pb composites were treated in the mechanical reactor for 4 h; the composite had granules of 0.7 to 1.2 mm.The mechanically alloyed composite was cold pressed to a density of 75% and then the compacts were annealed at 500ºC for 3 h. The semi-finished products were hot pressed at 400ºC with an elongation ratio of 10.Standard equipment and techniques were used to study mechanical properties and perform an x-ray analysis and optical and electron microscopy. Antifriction properties were studied using a 2070SMT-1 machine in disk-pin (counterface-sample) dry sliding friction; 18KhGT steel with a surface hardness of 58 to 60 HR...
