THE EFFECT OF QUENCHING ON THE MECHANICAL-PROPERTIES OF POWDER METALLURGICALLY PRODUCED AL-SIC (PARTICLES) METAL MATRIX COMPOSITES

Several factors contribute to the strengthening in particulate metal matrix composites (MMCs); their interdependence makes the elaboration of an exhaustive explanation of the phenomenon difficult. In the present work, a comparison between different powder metallurgically produced MMCs consistency of an aluminium matrix reinforced with SiC particles, both in the as-extruded state and in the quenched state, is carried out. Data concerning two powder metallurgy processes, four average particle sizes and four volume fractions of the reinforcement are analysed and compared with the unreinforced matrix. Such analysis allows a deeper understanding both about the result of the mismatch in between the thermal expansion coefficients of the matrix and of the reinforcement on dislocation density, and about the Al-SiC solid state reaction. These phenomena act on the strengthening mechanism. Their effect is very specific, because it strongly depends on the SiC particle average size and volume fraction. So, the difference between the ultimate tensile strengths of the as-extruded composites and the quenched composites can change case by case. Sometimes, the improvement in mechanical properties is excellent. This gives well-grounded encouragement in study and design of a suitable heat treatment for such MMCs.