Effect of testing temperature from cryogenic to high temperatures on dynamic fracture properties in 5083 aluminum alloy

Effect of temperature on mechanical properties of an 5083 aluminum alloy has been investigated for various testing temperatures from 10 to 773 K. For that purpose, the static tensile, dynamic fracture toughness test and fractography are carried out, and stop block method is employed to characterize fracture behavior at cryogenic temperatures. Mechanical properties such as 0.2% proof stress and ultimate tensile strength increase with decreasing temperature. The high temperature embrittlement, which has been often reported for 5000 series alloys having high Mg content, was not observed in the present study. The dynamic fracture toughness value, J_d, and dynamic crack extension toughness, T_mat, at 20 K are approximately 57% and 74% lower than that at 150 K, respectively. Fracture toughness at cryogenic temperatures shows strong dependence on formation of delamination cracks. The delamination cracks are initiated at grain boundaries. According to a SEM-EDX analysis, Mg is detected adjacent to the delamination cracks. Therefore, it is concluded that the formation of delamination cracks are concerned with β(Al₃Mg₂) phase at the grain boundaries.