High toughness and high strength spray-deposited AlCuMgAg-base alloys for use at moderately elevated temperatures

Chemical composition and heat treatments of spray-deposited AlCuMgAg-base alloys for use at ambient and moderately elevated temperatures have been optimized for high strength and high fracture toughness. This alloy development has led in particular to two new age hardenable aluminium alloys (N213 and N232) with excellent property combinations. N213 (AlCu5Mg0.4Ag0.4Ti0.4Zr0.15Mn0.2) clearly outperforms commercial 2XXX series alloys such as 2618 in terms of fracture toughness and yield strength at temperatures up to 180 °C. N232 (AlCu4Mg0.8Ag0.4Zr0.5Mn0.4) shows the highest product of yield strength and fracture toughness ever achieved for aluminium alloys; at 23 °C yield strength and fracture toughness values are RP0.2 = 378 MPa, KIC = 100 MPa m12 (T4 temper), and RP0.2 = 452 MPa, KIC = 77 MPa m12 (T6 temper). Fatigue strength of this experimentak akkits (T6 temper) is also obviously superior to that of commercial aluminium alloys such as 7475-T7351 and 2219-T8. N213 and N232 show stress corrosion cracking behaviour comparable with that of commercial 2XXX alloys; plateau crack growth rates around 10−8 m s−1 have been measured. ealed by transmission electron microscopy studies, the excellent property combinations of the new alloys can be related to microstructural characteristics, such as type, size, density and distribution of the precipitates. Moreover, these studies explain the nature of the microstructure tending towards overaging during extended exposure at temperatures above 150 °C; in particular the harmful impact of higher Mg contents on the microstructural stability at elevated temperatures is evidenced.