Research On The Creep Life Of Super-high-strength Aluminium Alloy

X aluminium alloy is a China-made super-high-strength aluminum alloy which is widely used in aviation and aerospace and other fields. As the main structure ma- terials of a special equipment, the life of the super-high-strength aluminium alloy is expected to be longer than 15 years. Because the super-high-strength aluminium alloy works in creep environment, it is essential to evaluate the creep life of the super-high-strength aluminium alloy.This research is based on the theory of classical material mechanics and fracture mechanics. The limited creep stress was tested by using standard specimen of the super-high-strength aluminium alloy under the work condition. A cylinder sample was used to get the creep rupture strength of the super-high-strength aluminium alloy. Notched cylinder was used to get the threshold stress intensity factor and the damage tolerance of super-high-strength aluminium alloy.The experimental results show that (1) the limited creep stress at 40℃after used 15 years is 495MPa. When the work stressσ<495MPa, the creep strain in 15 years is less than 1.5%, and the creep damage or the creep rupture doesn't occur. (2) The relationship between the creep rupture time and the stress, can be described asσ=-17.90lnt+717.18,γ=0.90. The creep rupture strength of the super-high-strength aluminium alloy at 40℃in 90% confidence is 508MPa±12MPa. When the work stress is less than 496MPa, the cylinder can operate safely longer than 15 years on the work condition. (3) The threshold stress intensity factor is 16MPa·m^1/2. The damage tolerance of the fish tail on the outer surface, the crack on the inner surface and the defect on the inner surface are 0.18mm, 0.24mm and 0.42mm respectively. The super-high-strength aluminium alloy cylinder can operate safely longer than 15 years on the work condition.