中文摘要：

通过单向拉伸实验在LA41镁合金中观察到了PLC（Portevin—Le Chatelier）效应．在整个实验的应变速率范围（3．33×10^-4-6．66×10^-3s^-1）内这种塑性不稳定性始终存在．合金的抗拉强度和屈服强度随应变速率的增加而减小，其应变速率敏感系数始终为负值，且该不稳定性总是在一个临界应变之后出现．基于以上特征，运用动态应变时效（dynamic strain aging，DSA）机制，即形变过程中溶质原子与可动位错的交互作用，解释了所观察到的力学现象．

英文摘要：

Uni-axial tensile deformation of LA41 magnesium alloy has been carried out and PLC （Portevin-Le Chatelier） effect, also known as serrated flow or plastic instability, is observed. This kind of alloy exhibits negative strain rate sensitivity （SRS） at room temperature, that is, SRS is negative at the strain rate range from 3.33×10^-4 to 6.66×10^-3 s^-1 at ambient temperature. Both ultimate stress （σb） and 0.2% proof stress （σ0.2） decrease with increasing strain rate, whilst critical strain （εc） of serrated flow is found to rise with enhancing strain rate. A new explanation for this unusual phenomenon is presented. The model of dynamic strain aging （DSA） is established though diffusion of solute atoms to mobile dislocations, which are temporarily arrested at obstacles. Such interaction renders the movement of mobile dislocations more difficult, consequently, necessitates the required force to overcome the obstacles.