Fatigue crack growth and wear behaviors in rheocast Al−Si−Mg alloys

Rheocast aluminum alloys, which consist of globular α-Al cells, refined grains and eutectic Si particle, were used to investigate fatigue crack growth and wear characteristics. The Si particles were systematically varied from coarse and acicular shapes to small and globular ones. At low ΔK fatigue crack growth rates decreased in samples consisting of acicular Si particles of large grain size, which induced a large amount of crack closure. Large and acicular Si particles were easily cracked and separated the particle/matrix interface, which promoted to fracture at smaller ΔK. On the other hand, small Si particles made fatigue crack grow, even at a high ΔK region, and increased the fracture toughness of the alloy. However, in the wear test, small eutectic Si particles were pulled out by friction force during sliding wear and the wear loss amount increased with increase in sliding distance.