抄録
The rotating bending high cycle and the push-pull low cycle fatigue tests were performed on the cold-worked Al-2.4% Mg alloy, and its fatigue properties were examined and compared with those of the solution-treated one reported previously in another paper.
The cold-worked Al-2.4% Mg alloy did not show the cyclic softening during cyclic straining. This fact might be closely associated with the strong dynamic strain ageing property of the present material. The cyclic stress-strain relation was not influenced by the amount of the reduction given to the material.
The cold-work reduced the low cycle fatigue life of the solution-treated alloy, but it did not depend on the reduction ratio, as in the cyclic stress-strain relation. On the other hand, the exponent, α, in Manson-Coffin's law of Δεp·Nfα=C, which is also applicable to the present material, was about 0.84 and 0.64 for the solution-treated and the cold-Worked Al-Mg alloy, respectively. The difference in the value of α can be interpreted by considering the deformation mode of the two materials: the slip is concentrated at and near the grain boundary in the former, while it is uniformly dispersed, independent of grain boundary, in the latter.
The effect of the cold-work on the high cycle fatigue strength of the Al-2.4% Mg alloy was very small, compared with those of other metal materials. This might be due to the small inclusions contained in the material, from which fatigue crack originates.
