铝合金PLC效应与声发射特性的实验研究

考虑退火温度和应变率对6063铝合金力学性能的影响，采用材料试验机和声发射测试系统对铝合金PLC效应和声发射特性开展实验研究，获得了不同应变率下材料的应力-应变曲线和不同退火温度下声发射参数的变化规律.结果表明，2×10-3，2×10-4，2×10-5s-1应变率加载时，6063铝合金的应力应变曲线表现出明显的PLC现象，降低加载应变率，PLC现象增强，并出现了从A型到C型的转化；加载应变率为2×10-4s-1时，PLC效应的临界应变随退火温度的升高而降低；由于细观结构上可动位错密度的增加，屈服阶段试件中产生的声发射振铃计数急剧增加，达到峰值；进入到塑性强化阶段，声发射活动减弱；弹性变形阶段和塑性强化阶段产生突发型信号，而屈服阶段为连续型信号，与试件的均匀变形以及剪切变形带的形成与传播相关. 

Experimental Study on PLC Effect and Acoustic Emission Characteristics of Aluminum Alloy

Considering the influence of annealing temperature and strain rate on the mechanical properties of 6063 aluminum alloy, the PLC effect and acoustic emission characteristics of aluminum alloy were experimentally studied by material testing machine and acoustic emission testing system. The stress-strain curves of materials under different strain rates and the variation of acoustic emission parameters at different annealing temperatures were obtained. The results show that the stress-strain curves of 6063 aluminum alloy exhibit obvious PLC phenomenon when loaded at strain rates of 2×10^-3, 2×10^-4 and 2×10^-5 s^-1. When the strain rate is reduced, the PLC phenomenon is enhanced, and the conversion from type A to type C occurs. The critical strain of the PLC effect decreases with the increasing annealing temperature at 2×10^-4 s^-1. With the increase of the dynamic dislocation density on the mesostructure, the acoustic emission ringing count increases sharply and reaches the peak value in the yield stage. The acoustic emission activity is weakened in the plastic hardening stage. The burst type signal is generated in the elastic stage and the plastic strengthening stage, while the continuous signal is generated in the yield stage, which is related to the uniform deformation of the specimen and the formation and propagation of the shear deformation zone.