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本工作进行了淬火Al-7.27％Ag合金的扭转疲劳试验,测定了各种扭应变下的 △E-N曲线,并且观察了经过各种循环数以后试样的表面金相变化。 实验结果指出,当扭应变较小时,△E随着循环数N的增加而逐渐下降,△E-N曲线的变化类似Al-Cu和Al-Mg合金在较低扭应变下的情况。但当扭应变较大时,△E开始略有下降,随后上升到某一较高值后再下降,直至试样断裂。△E-N曲线的形状与Al-Cu和Al-Mg合金完全不同。试样表面的金相变化分为两个明显不同的阶段。在疲劳的起始阶段,滑移痕迹细而均匀,但经过一定循环数后,少数滑移痕迹变得集中而深化。随着循环数的增加,新的滑移带在原有滑移带之间不断地出现,没有纯Al和Al-Mg合金中滑移带变宽的情况。还看到了裂纹沿晶界的形成和发展。 根据溶质银原子与位错的电交互作用和位错切割银原子簇的观点,对所得到的结果进行了讨论。
In this work, the torsional fatigue test of Al-7.27% Ag alloy was carried out. The △ E-N curves were measured under various torsional strains, and the surface metallurgical changes of the samples after various cycles were observed. The experimental results show that when the torsional strain is small, ΔE gradually decreases with the increase of the number of cycles N, and the change of △ E-N curve is similar to that of Al-Cu and Al-Mg alloys under low torsional strain. However, when the torsional strain is large, ΔE begins to decrease slightly, and then rises to a higher value before descending until the specimen breaks. The shape of the ΔE-N curve is completely different from that of Al-Cu and Al-Mg alloys. The metallographic changes on the specimen surface are divided into two distinct phases. In the initial stage of fatigue, the slip marks are fine and even, but after a certain number of cycles, a few slip marks become concentrated and deepened. With the increase of the number of cycles, the new slip band continuously appears between the original slip bands without the widening of the slip band in pure Al and Al-Mg alloys. Also seen the formation and development of cracks along grain boundaries. The results obtained are discussed based on the electrical interaction of solute silver atoms with dislocations and the dislocation of silver clusters.