アルミニウム多結晶材の疲労過程における転位組織と疲労硬化の関係

概要

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Push-pull and plane bending fatigue tests in the high cycle fatigue region were carried out on annealed polycrystalline pure aluminum. The relationship between fatigue-induced dislocation structures and macroscopic hardening (unidirectional and cyclic) was investigated in the whole process of fatigue before the initiation of macro-crack. The stress amplitude σ_a and the plastic strain range Δε_p tended to saturate at the early stage of fatigue in the both strain control- and stress control-tests. On the other hand, the Vickers hardness H_v, the dislocation bundle width B_w and the dislocation density ρ increased gradually until the initiation of macro-crack. Such behaviors of σ_a and Δε_p can be explained from the dislocation shuttling model for the mobile dislocations, and the behaviors of H_v, B_w and ρ from the increase of the immobile dislocations. Furthermore, it is shown that the relationship between H_v and ρ is expressed as H_v-H_<vo> = C_3 (ρ-_0)^h where H_<vo> and ρ_0 are the values of H_v and ρ at the annealed state, respectively, and C_3 and h are the experimental constants.
1978-03-15