耐応力腐食割れ性に優れた高力Al-Zn-Mg-Cu-La系押出合金の疲労き裂伝ぱ特性

概要

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Fatigue crack growth tests on an extruded Al-8 wt.% Zn-2.5 wt.% Mg-1.2 wt.% Cu-4 wt.% La alloy were carried out using CT specimens(TL orientation). Crack closure was examined by the unloading elastic compliance technique. The main results are as follows; (1)The effect of stress ratio was observed on the crack growth rate, da/dN, vs.stress intensity factor range, ΔK, diagram. A higher stress ratio gives a faster crack growth rate at same ΔK. (2)Crack closure was observed under the stress ratio=0.1, and its degree was increasing with decreasing stress intensity factor range. On the other hand, it was not at the stress ratio=0.5. (3)The effect of stress ratio on the second region of da/dN vs.ΔK diagram disappeared when the effective stress intesity factor range, ΔK_<eff> was used instead of ΔK. (4)The second region of da/dN vs.ΔK_<eff> diagram for the extruded Al-8 wt.% Zn-2.5 wt.% Mg-1.2 wt.% Cu-4 wt.% La alloy was in agreement with that for the commercial 7075T6 alloy. So, the fatigue crack growth resistance of the extruded Al-8 wt.% Zn-2.5 wt.% Mg-1.2 wt.% Cu-4 wt.% La alloy is nearly equal to that of the commercial 7075T6 alloy.
社団法人日本材料学会の論文
1995-02-15