Comparison of fracture in sheets of low pressure gas (LPG) steel and aluminium alloys

Fracture behaviour under different stress states of four heats of hot rolle d low pressure gas (LPG) grade steel and three 1 mm thick cold rolled alumi nium alloys (Al-Cu-Mg, AI-Mg and AI-Mn) is compared. Dimple fracture was pr esent in all four materials but the dimples were larger and of more uniform size in LPG steel compared with those present in the Al-alloys. Depending on the relative strength of pearlite and pearlite-matrix interface, failure in LPG steel was either transgranular or ductile intergranular. In the Al- alloys, particle-matrix decohesion was always responsible for dimple format ion and transgranular fracture. In the Al-Cu-Mg and AI-Mg alloys a bimodal dimple size distribution, traceable to precipitates of two different sizes, was present but in the AI-Mn alloy the dimple size was larger and of nearl y the same size. The results are explained in terms of composition, microst ructure and mechanical properties of the alloys. (C) 2001 Elsevier Science B.V. All rights reserved.