THE EFFECTS OF PARTICLE SIZE ON SMALL CRACK GROWTH IN SIC PARTICULATE-REINFORCED ALUMINUM ALLOY COMPOSITES

摘要

Fatigue crack initiation and small crack growth behavior were studied in powder metallurgy 2024 aluminum metal-matrix composites reinforced with three different sizes of SiC particles (5 μm, 20 μm and 60 μm) under axial loading. The 5 μm and 20 蘭 SiC_p/Al composites exhibited nearly the same fatigue strength as the unreinforced alloy, while the 60 μm SiC_p/Al composite showed lower fatigue strength due to its inferior crack initiation resistance. Small crack growth behavior depended on stress level. At a low stress level, addition of SiC particles increased the growth resistance, particularly in the composites reinforced with coarser particles, while at a high stress level, the 60 μm SiC_p/Al composite showed faster crack growth rates, which could be attributed to interference and coalescence of multiple cracks.