Fracture toughness of 6061 and 7N01 aluminum alloy welded joints for high-speed train

According to Chinese Standard GB/T 21143-2007 Metallic materials-Unified method of test for determination of quasistatic, the fracture toughness CTOD value δ_c and J integral value J_c in different areas of the welded joints of 6061 and7N01 aluminum alloys commonly used in high-speed trains were obtained. Using mathematical and statistical methods, the fracture toughness of the welded joints and the relationship between fracture toughness, microstructure and fracture morphology were analyzed. The results show that logarithmic normal distribution was best fitted for fracture toughness data acquired from small samples. Generally, δ_c and J_c in both 6061 and 7N01 aluminum alloy welded joints had the maximum values in the HAZ, followed by in WM and BM. However, δ_c and J_c in BM and WM of7N01 aluminum alloy welded joint were greater than those of6061 aluminum alloy welded joint. δ_c in HAZ of 6061 aluminum alloy welded joint was greater than that of 7N01 aluminum alloy welded joint, while J_c in HAZ of 7N01 aluminum alloy welded joint was better than that of 6061 aluminum alloy welded joint.