Tensile and fatigue properties of a thermomechanically treated 7475 aluminium alloy

Study of fatigue behaviour of 7475 aluminium alloy

“…In aluminium alloys, constituent particles provide sites for fatigue crack initiation. As outlined by Suresh (1996), and Jahn and Luo (1988), the relative probability of crack initiation increases with particle thickness. It has also been cited that the surface grains are the most probable location for crack initiation in metals and alloys of high purity.…”

“…The fracture surface of the same specimen at 375 µm from the crack originating surface reveals ductile striations and tearing ridges; a high energy fracture. This is an indication of high toughness material which has excellent resistance to fatigue crack propagation (figure 6b) (Jahn and Luo 1988). It also appears that no secondary crack is present in the examined region (figures 6a and b).…”

“…Under such conditions, the stresses are more uniformly distributed across the specimen and hence reduce stress concentration on insoluble particles. This may delay the crack initiation and results into better S-N curve performance (Jahn and Luo 1988). It may also be concluded from the observation that 7075-T6 is not a suitable alloy for applications where high tensile stresses are expected.…”

“…Properties in 7075 alloy are improved by reducing its contents of iron and silicon, and altering quenching and ageing conditions. These modifications in 7075 alloy result in the development of 7475 alloy having fine grain size, optimum dispersion and highest toughness value among the aluminium alloys commercially available at high strength level (Jahn and Luo 1988). It is also reported that the corrosion resistance and corrosion fatigue behaviour of 7475 alloy are excellent (Jahn and Luo 1988).…”

“…These modifications in 7075 alloy result in the development of 7475 alloy having fine grain size, optimum dispersion and highest toughness value among the aluminium alloys commercially available at high strength level (Jahn and Luo 1988). It is also reported that the corrosion resistance and corrosion fatigue behaviour of 7475 alloy are excellent (Jahn and Luo 1988). In general, its performance is better than that of many commercially available high strength aerospace aluminium alloys such as 7050 and 7075 alloys.…”