FRACTURE TOUGHNESS IN Al—Mn ALLOYS

Abstract

An investigation has. been - carried out to study the effect of mechanical and thermal treatments on mechanical properties and fracture toughness of Al-0.91 Mn-0.43 Si-0.30 Fe alloy. The alloy was homogenised and cold deformed to 20 pct, 50 pct and 70 pct deformation by rolling. Subsequently , annealing treat-menta were given for ,- hour and 20 hours. The changes in tensile properties, frac-6ure mode and dimple size with the above variables have been studie-e.. The fracture mode was found to be cup and cone type irrespective of the pct deformation and heat treatment given. The strength and fracture toughness Values for the alloy under investigation show an increase upto 50% deformatiyon by rolling. Deterioration in mechanical properties and fractwre toughness values results at 70 pct deformation Finally,an attempt has been made to correlate the fracture toughness values with the dimple size. For this alloy there is no recognized test for directly measuring fracture mechanics indices because it has very low strength and is extremely ductile. Fracture is initiated in this alloy at the interfaces between matrix and precipitate particles