Low-temperature creep behavior and microstructural evolution of 8030 aluminum cables

The creep behavior and microstructural evolution of 8030 alloy at 90-150 °C and 50-90 MPa of applied tensile stress were investigated by creep testing and transmission electron microscopy. The 8030 alloy possesses excellent creep resistance at low temperatures. The sizes of a small number of subgrains increase during the creep process due to subgrain merging. An Al3Fe phase non-uniformly pinned on the subgrain boundary made the pinned subgrains difficult to merge with the surrounding subgrains. At 90-120 °C/50-90 MPa, the stress exponent n was 5.1-5.7 and the activation energy Qc was 49.7-66.5 kJ/mol, suggesting that dislocation climb controlled by the grain boundary diffusion is the primary creep mechanism. At 150 °C, the ability of Al3Fe secondary phase to hinder the dislocations significantly decrease. When the tensile stress is 50-70 MPa, n = 6.8 and Qc = 49.7-66.5 kJ/mol, but n = 10.0 at a stress of 90 MPa. A creep activation energy of 123.2 kJ/mol is close to that of the lattice self-diffusion in aluminum, implying that a lattice self-diffusion mechanism is dominant at 150 °C/90 MPa.