Research Organizations And Heat Resistance Al-Cu-Mg- (Ag) Alloy Fatigue Properties

Al-Cu-Mg-Ag alloys were promising in aircraft applications due to high thermal stability and fatigue properties. The microstracture and thermal stability, as well as the effect of silver on the growth of Ω plates were systematically analyzed and discussed in detail. Meanwhile, the heat resistant properties of Al-Cu-Mg-Ag alloy containing Fe、Ni elements were investigated. In addition, the influence of texture on the fatigue behavior of several2524-T351alloys was examined. The main conclusions can be summarized as follows:(1)The tensile properties of165℃/14h treated Al-Cu-Mg-Ag alloys were superior at room temperature and200℃than that of165℃/2h, whereas at250and300℃,165℃/2h samples had greater tensile strength.(2)During exposure at200℃, the drop in tensile strength was less significant in the165℃/14h aged Al-Cu-Mg-Ag alloys for the reason that the lengthening rate of Q. plates was lower and the number density of Ω precipitates was greater in the165℃/14h aged samples than the165℃/2h aged ones. After exposure for1000h, seventy percent of the tensile strength were maintained in the165℃/14h aged samples. In both the165℃/14h and165℃/2h aged Al-Cu-Mg-Ag alloys, the thickening rate of Ω plates was very low during exposure at200℃and the growth behavior was exhibited mainly by the lengthening of Ω plates within the habit plane. High content of silver resulted in a higher segregation of Ag-Mg co-clusters in the interface of Ω plates and the matrixl. As Ag is heavy atoms, the segregation of co-clusters hindered the diffusion of atoms, which was disadvantage to the ledge migration, and inhibited the thickening of Ω plates.(3) The peak-aging state of Al-Cu-Mg-Ag-Fe-Ni alloys exhibited good performance at elevated temperatures. The tensile strength was415MPa and200MPa at200℃and300℃, respectively.(4) Goss texture was favorable to the fatigue properties of2524-T351alloys. Most{111} planes in alloys containing Goss texture were located close to the direction of the maximum shear stress, which promoted the movement of dislocations. The slip of dislocations resulted in the formation of persistent slip bonds (PSB) and the introduction of plasticity-introduced crack closure effect, as well as the reduction of damage accumulation, resulting in a smaller step of crack propagation under each stress cycle, and the reduction of fatigue crack growth rate.