Effects of Sintering Atmosphere on the Mechanical Properties of Al-Fe Particle-Reinforced Al-Based Composites

Al-based composites reinforced by Al-Fe intermetallic compounds have been fabricated by powder metallurgy technique. The reinforcements were formed in the aluminum matrix by in situ solid-state reaction between pure Al and pure Fe powders. The effects of sintering atmosphere on the microstructures and mechanical properties of the composites were systematically studied by scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction analysis, and compressive tests. It has been shown that Al-Fe intermetallic particles (including a large number of the Fe-Al₅Fe₂ core-shell structured particles) were the dominant reinforcements in the composites sintered under Ar atmosphere, while pure Fe particles were the dominant reinforcements in the composites sintered under N₂ atmosphere. N₂ atmosphere is more effective than Ar atmosphere in increasing the sintered density of the composites due to the formation of aluminum nitride, which can effectively fill the pores. Thus, the compressive mechanical properties of the composites sintered under N₂ atmosphere are higher than those of the composites sintered under Ar atmosphere.