Strength and fracture toughness of spray formed Al-Cu-Mg-Ag alloys

Spray formed Al-4.5Cu-Mg-Ag alloys with small additions of titanium, zircon ium, and manganese show improved mechanical properties compared with conven tionally produced alloys of the same class. In particular the combination o f strength, fracture toughness, and microstructural stability at elevated t emperature is clearly superior. At room temperature, typical yield strength values of over 420 MPa, elongations to fracture of 13%, and fracture tough ness values of 75-85 MPa,m(1/2) in the peak aged condition have been measur ed. Good thermal stability up to 453 K (180 degrees C) can be achieved by l imiting the magnesium content to values below 0.4 wt-%. Compared to the com mercial heat resistant alloy 2618-T61, spray formed Al-Cu-Mg-Ag alloys offe r higher strength after 1000 h exposure to temperatures up to 423 K (150 de grees C). In addition, they clearly exceed 2618-T61 in terms of fracture to ughness. The high yield strength is mainly attributed to fine and densely d istributed precipitates of Omega and Theta' phases, and the fine unrecrysta llised grain structure. This structure is stabilised by a fine distribution of zirconium containing dispersoids. An additional contribution to strengt h call be given by cold work before artificial aging. The fracture toughnes s can be improved by limiting the content of coarse copper and zirconium co ntaining constituents. This is achieved by control of chemical composition and processing. MST/3940.