Trace Of Ge, Ce On Al-cu-mg-(li) Alloy Microstructure And Properties

In this paper, Optical metallographic microscope (OM), Scanning electron microscopy (SEM),Transmission electron microscopy(TEM), high resolution TEM (HRTEM)observations, Micro Vickers hardness testing, tensile properties testing methods were employed. The effects of small additions of Ge,Si and Ge on the mechanical properties and aging characteristics of low Cu:Mg ratio Al-Cu-Mg alloys were studied systematically. A detailed study on the effect of additions of Ce on the microstructure and properties of 2524 alloy and 2198 alloy also were carried out. The main conclusions were as follows:(1)The precipitation hardening response and strength of the low Cu:Mg ratio Al-Cu-Mg alloys is enhaced by the additions of Ge. Compared with the alloy with 0.25%Ge or 0.5%Ge, the former has the higher strength. The addition of 0.25%Ge and 0.25% Si inhibited the aging response of the the low Cu:Mg ratio Al-Cu-Mg alloys.(2)Trace addition of Ge stimulates the formation of a fine and uniform dispersion of T phase. Trace addition of 0.25% Si and 0.25%Ge stimulates the precipitation of S phase.(3) Trace addition of Ce in 2524 alloy exhibit significant improvement on the fatigue crack propagation resistance, and prolong steady expansion stage. 2524 alloy enter into the instantaneous fracture stage while the alloy with trace Ce addition was still in the later period of steady expansion stage. The more of the addition of Ce,the better of crack propagation resistance.(4)Trace addition of 0.05% Ce has favourable effect on fatigue crack propagation resistance and fracture toughness of 2198 alloy at T6 condition,but addition of 0.1% Ce has unfavourable effect.(5)Trace addition of Ce in 2198 alloy stimulates the precipitation of T1 phase and their dispersive distribution, decrease the precipitates from grain,and addition of 0.05% Ce has favourable effect on the reduction.