Toughness and fatigue behaviour of eutectic and hypereutectic Al-Si-Cu-Mg alloys produced through lost foam and squeeze casting

摘要

The strength and toughness of four high silicon content Al-Si-Mg-Cu alloys have been studied at room temperature (RT), 200℃ and 300℃. The fatigue behaviour has also been investigated. The alloys were produced using two very different processing routes: lost foam and squeeze casting. In the tensile tests, the ductility was low for alloys produced via both routes irrespective of the testing temperature. The strength was similar at RT and 200℃, but at 300℃ it fell abruptly. The toughness followed the same trend with testing temperature. Direct observation of fatigue cracks revealed that the brittle silicon and intermetallic particles broke ahead of the crack tip; the fatigue crack advanced by linking the main crack with cracks formed ahead of it. The T6 thermal treatment improved fatigue resistance in the squeeze cast material, especially at high AK values.