Study of mechanical properties of high volume fraction aluminum/steel shots metal matrix composites

Abstract

In this study, aluminum metal matrix composites with different sizes steel shots were produced by squeeze casting method. First, steel shots preforms (0.2–2 mm) were made with and without sintering. Some of the preforms were sintered in an electric furnace at 1000 °C for 2 h. Then, the preforms were placed in steel die with molten aluminum and infiltrated by squeeze casting method. After composite making, microstructure of the composites was studied by optical microscope which showed the features of a homogeneous microstructure, uniformly distributed particles and no visible macrospores. The micrographs also showed that the steel shots were sintered successfully. Furthermore, the hardness, compressive strength and impact strength of the composites were also evaluated. The hardness of the composites clearly increased with smaller steel shots and it was much higher for the composites with sintered shots than nonsintered ones; the composites with 0.2 mm sintered steel shots showed the maximum microhardness (about 180 VHN). The compression tests also showed that the compressive strength of the composites increases by about 50% for the sintered steel shots. The impact results of the composites showed that the impact strength decreases with smaller sintered steel shots. The fracture surface of the impact samples were studied using scanning electron microscope. The fractured interparticle necks were also investigated in the composites containing sintered steel shots. As a result, interconnection of the reinforcement particles is a very efficient way to improve the mechanical properties of the metal matrix composites.