2013 Volume 54 Issue 12 Pages 2195-2201
It has been reported that most aluminum alloys contain high-density micro pores, which make an appreciable contribution to damage evolution during ductile fracture. It is reasonable to assume that the mechanical properties of aluminum alloys are more or less improved by controlling micro pores in aluminum alloys. In the present study, the volume fraction of micro pores is controlled by controlling hydrogen content over a wide range. Tensile tests are performed using smooth and notched specimens at room and elevated temperatures, together with a fracture toughness test. It has been shown that both strength and ductility increase with decreasing micro pore volume fraction. The elimination of micro pores has pronounced effects especially on high-temperature ductility, notched tensile strength and fracture toughness. It has been observed in the in-situ observation of a room temperature tensile test that pre-existing hydrogen micro pores exhibit premature growth immediately after the onset of plastic deformation, whereas the well-known particle fracture mechanism operates only after the maximum load in the alloys with the least micro pores fraction. It can be inferred that in the notched and pre-cracked specimens, the premature growth of micro pores are driven by triaxial stress state, thereby inducing more degradation in mechanical properties.