自然时效对6061铝合金锯齿形屈服的影响

Study on the influence of nature aging on serrated yielding of 6061 Al-based alloy

摘要:

对固溶处理淬火后自然时效时间不同的6061铝合金在室温下进行恒定应变率的拉伸实验,研究了自然时效对Portevin-Le Chatelier(PLC)效应的影响。实验发现,材料强度、锯齿周期和临界应变三者在自然时效0~1 h期间均无明显变化,在自然时效超过1 h以后随自然时效时间延长而增大；锯齿幅值在自然时效0~2 h期间随自然时效时间延长而减小,在自然时效超过2 h后趋于稳定值。自然时效过程中,强化效果明显的β""相在自然时效时间1~2 h之间开始形成并随自然时效时间线性增加。结合动态应变时效模型的分析结果与实验相符合,揭示了有强化效果的析出相对PLC效应的作用机制：具有强化效果的析出相含量增多将缩短可动位错的等待时间,使得可动位错更难被钉扎,从而导致锯齿周期和临界应变增大。分析结果还表明,该合金中溶质原子主要以体扩散方式向可动位错聚集从而实现对可动位错钉扎。

Abstract:

The influence of nature aging (NA) on the Portevin-Le Chatelive (PLC) effect was investigated via tension tests in solution treated 6061 Al alloy. The yielding strength, the tensile strength, the critical strain and the serration period changed little in the NA time range of 0~1 h and then increased with increasing NA time. The serration amplitude decreased in the NA time range of 0~2 h and kept constant over 2 h. The precipitation sequence of the alloy suggests that the precipitates that can significantly strengthen the alloy formed after NA for 1 h and increased linearly with NA time. These precipitates inhibit the dislocation motion and result in shortening the waiting time. It is more difficult to produce the pinning process and thus the serration period and the critical strain increase. Moreover, the solute atoms gather to mobile dislocations by body diffusion rather than pipe diffusion in this alloy.