Effect of stress concentration on the fatigue and corrosion-fatigue properties of cast aluminum VAL10 and forced aluminum AK6 alloys

Abstract

1. The fatigue resistance of cast aluminum alloy VAL10 depends on the degree of casting porosity. There is no marked anisotropy in the fatigue properties of alloy AK6 in relation to texture direction. 2. Under the action of stress concentration (notch r=1 mm) the fatigue limit of alloy AK6 is reduced by 36–40% and it is almost independent of test base. For alloy VAL10 this reduction in fatigue limit depends on test base, and it is 24% with N=5.104–106 cycles and 24–40% with N=10–20·106 cycles. 3. The reduction in alloy AK6 endurance with presence of a notch is almost identical for specimens with longitudinal and transverse orientation of the texture. 4. With an increase in alloy VAL10 specimen porosity the degree of the effect of stress concentration on endurance is reduced, which may be explained by an increase in the relieving effect connected with an increase in pore number and size. 5. Under conditions of simultaneous operation of stress concentration and corrosion medium the reduction in fatigue limit for alloy AK6 is 45–53% in the test endurance range, both for specimens of longitudinal and transverse orientation of the texture. 6. It was established that a corrosive medium has practically no effect on the endurance of notched alloy VAL10 specimens in the cyclic loading range 32–70 MPa. With endurances less than 70·106 cycles, the corrosion-fatigue resistance of alloy VAL10 under the action of stress concentration is greater than for alloy AK6 (across the fibers).