Impact of the Structure on Mechanical and Tribological Properties of Sintered (Al–12 Si)–40 Sn Alloy

Abstract

Interaction of the structure of the composite alloy (Al–12 Si)–40 Sn with its mechanical and tribological properties was studied. The alloy was obtained by the liquid-phase sintering of powder briquettes made of the powder mix of tin PO-2 and an atomized aluminum alloy of the eutectic composition Al–12 Si. Sintering was carried out at a temperature below the melting point of the eutectic; otherwise, the sample melted and lost its shape. It was found that the given sintering temperature does not make it possible to obtain samples with high density; their residual porosity was 6–8% and it almost was not decreased with the increase in the sintering time. The obtained material had low mechanical properties, which slightly improved with the increase in the sintering time to two hours. At the same time, the amount of exuded and evaporated tin noticeably increased. Taking into account the undesirable phenomena that occurred during a long exposure of sintered samples at high temperature, the hot densification was carried out after the short-term sintering. Densification of the sintered samples aiming at removal of the residual porosity was carried out in a closed mold under pressure above the ultimate strength of the alloy. It was established that such operation contributed both to significant improvement of strength and ductility of the studied material. In addition, the obtained nonporous material had high wear resistance under dry friction against a steel counterbody; it was especially noticeable during friction under high pressure. The wear rate of samples with a matrix made of the aluminum-silicon alloy was 30% lower as compared with the alloy with the matrix made of pure aluminum at all other conditions being equal.