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本文进行了淬火状态的、含0.52,0.91,3.46和5.15％Mg的铝合金的扭转疲劳试验,测定了相应的ΔE-N曲线和T_m-N曲线。实验结果指出,对于含镁量为0.52,0.91％的试样来说,当表面扭应变较小时,ΔE在起始时,随着应力循环数的增加而下降。当表面扭应变增大时,ΔE-N曲线始而变平,继而上升,直至达到一较高值才稳定下来。当试样中的含镁量为3.46％时,在扭应变不太大时,ΔE-N曲线的变化情况与Al-4％Cu合金的相象,不过当扭应变足够大时,ΔE起始时上升,并且经过一个峯值又下降。当含镁量增至5.15％时,ΔE-N曲线的表现已完全与Al-4％Cu合金的相象,在所用的最高表面扭应变下也并不表现出明显的峯值。对于所用的各种成分的试样来说,最大抗扭矩T_m起始总是上升的。 上述结果都可以根据溶质镁原子在疲劳过程中渐渐进入位错,形成气团来解释。可以认为,在铝镁合金的情形,产生ΔE的因素以及影响ΔE的大小的因素,对于疲劳载荷的起始阶段来说,可能都主要是由于气团的作用。当含镁量较低时,对于足够高的表面扭应变来说,气团较为松动,位错能够拖着气团运动,从而需要作功,使ΔE和T_m都上升。但当合镁量较高时,或表面扭应变不太大时,在疲劳一起始就形成了能够对于位错起钉扎作用的足够浓的气团。继续进行疲劳时,进入位错的溶质原子将
In this paper, the torsional fatigue tests of quenched aluminum alloys containing 0.52, 0.91, 3.46 and 5.15% Mg were carried out and the corresponding curves of ΔE-N and T_m-N were measured. The experimental results show that, for the samples with 0.52 and 0.91% of Mg content, ΔE decreases at the beginning as the number of stress cycles increases when the surface torsional strain is small. As the surface torsional strain increases, the ΔE-N curve initially flattens and then rises until it reaches a higher value before it stabilizes. When the content of Mg in the sample is 3.46%, the change of ΔE-N curve is similar to that of Al-4% Cu alloy when the torsional strain is not too large, but when the torsional strain is large enough, ΔE starts It rises and falls through a peak. When the magnesium content increased to 5.15%, the ΔE-N curve behaved exactly like the Al-4% Cu alloy, and did not show any significant peak at the highest surface strain. For the various components of the sample used, the maximum torque T_m always begins to rise. These results can be based on solute magnesium atoms gradually into the dislocation during fatigue, the formation of air mass to explain. It can be considered that in the case of aluminum-magnesium alloy, the factors that produce ΔE and the factors that affect the size of ΔE may be mainly due to the role of the air mass for the initial stage of fatigue load. When the magnesium content is low, the air masses are loose and the dislocations can drag the air mass for sufficiently high surface torsional strain, which requires work to increase ΔE and T_m. However, when the amount of magnesium is higher or the surface strain is not too great, a sufficient concentration of air mass capable of pinning the dislocations is formed at the beginning of fatigue. When fatigue continues, the solute atoms that enter the dislocations will be