铝合金具有优良的物理和力学性能，广泛应用在各工业领域，但其应用受到锯齿形屈服现象，即Portevin-Le Chatelier(PLC)效应的严重制约。先前研究主要关注轴向变形、应力锯齿和宏观唯像模型等方面，目前在三维变形特征、临界机制、跨尺度建模等问题尚需更深入更全面的理解和认识。针对这些问题，本项目以在研新型5000系铝合金为对象，对其锯齿形屈服空间变形和临界机制开展实验研究和理论分析。1)实验观测 PLC带的三维空间变形行为，分析空域变形和应力锯齿之间的对应关系；2)建立 “温度-应变率”空间下的临界应变机制，预测多种合金临界应变演化规律；3)建立反映微观物理机制并再现宏观力学行为的跨尺度力学模型。研究结果有助于完善锯齿形屈服的临界机制，提供新的认识角度，加深对其物理本质的理解，为进一步寻求抑制PLC效应的方法和改善合金设计奠定基础。

As they have excellent physical and mechanical properties, aluminum alloys are widely used in industry. Unfortunately, their application is still restricted due to serrated yielding, i.e. the Portevin-Le Chatelier (PLC) effect. Previous studies of serrated yielding mainly focused on the axial deformation, stress drops and phenomenological model. However, some issues such as the feature of 3D-deformation, the critical mechanism, the multi-scale modeling, etc. are not clear yet. In this project, these issues will be investigated by the following researches. 1) The 3D-deformation of the PLC band will be observed and the relationship of “deformation-serration” will be presented. 2) A critical mechanism will be established in “temperature-strain rate” domain to forecast the behavior of the critical strain for 5000 Al alloys. 3) A multi-scale model will be proposed to reflect the physical mechanism on micro scale and to reproduce the mechanical behavior on macro scale. The expected results will present a new understanding of serrated yielding and provide the theory support for the development in alloy design.