Influence of severe plastic deformation on dynamic strain aging of ultrafine grained Al-Mg alloys

本课题的目的是：1)探索SPD加工对UFG Al-Mg合金DSA和PLC效应的影响；2)探索DSA和PLC效应对sdp加工UFG Al-Mg合金变形行为的影响。在第一阶段进行的调查显示，外在SPD处理对DSA的强烈影响，以及内在DSA对as-SPDed UFG Al-Mg合金在室温下的变形行为的影响（见本申请第1节中列出的第一阶段的工作报告和项目相关出版物[1]）。为了对这些复杂的相互作用有更深入的物理认识，在实验结果的基础上进行理论分析必须在第二阶段进行。为此，将利用最近开发的粗晶/小应变FCC合金的DSA模型和FCC金属和合金在非常大应变下的应变硬化模型。然而，它们必须加以修正，以解释as-SPDed Al-Mg合金中急剧细化的晶粒尺寸，严重增加的位错密度以及因此而增强的溶质扩散系数。模型修正所必需的微观结构、力学和热力学数据将取自实验结果。因此，在第二阶段，实验研究将从RT扩展到更高的温度（分别为50°C， 100°C， 200°C和300°C）。通过智能显微组织和力学实验研究，获得as- spded UFG Al-Mg合金在高温下的显微组织演变和力学行为信息，以及控制DSA强度和动力学的热力学参数，如溶质扩散系数、变形活化能/溶质原子之间的结合能和捕获的移动位错。在理论模型预测和实验结果的基础上，建立了限制UFG Al-Mg合金（例如Al-1Mg和Al-5Mg）在温度为RT ~ 300℃、应变速率为10-5s-1 ~ 10-5s-1时DSA/PLC效应范围的各自域。

The purpose of the proposed project are 1) to explore the influence of SPD processing on DSA and the PLC effect of UFG Al-Mg alloys and 2) to explore the influence of DSA and the PLC effect on the deformation behavior of SDP-processed UFG Al-Mg alloys. Investigations carried out during the first period revealed a strong influence of both extrinsic SPD processing on DSA and intrinsic DSA effect on the deformation behavior of as-SPDed UFG Al-Mg alloys at room temperature (see the work report and the project-related publication [1] for the first period listed in the section 1 of this application). In order to gain a deeper physical insight into these complex mutual interactions, performed theoretical analysis based on the experimental results must be conducted in the second period. For this purpose, recently developed models for DSA in coarse grained/small strained FCC alloys and strain hardening at very large strains of FCC metals and alloys will be utilized. However, they have to be modified to account for the drastically refined grain size, the severely increased dislocation density and consequently, an enhanced solute diffusivity in the as-SPDed Al-Mg alloys. The microstructural, mechanical and thermodynamic data which are necessary for the model modifications will be taken from the experimental results. Therefore, in the second period the experimental investigations will be extended from RT to elevated temperatures (at 50 °C, 100 °C, 200°C and 300 °C, respectively). The information of microstructural evolution and mechanical behavior of as-SPDed UFG Al-Mg alloys at elevated temperatures, as well as thermodynamic parameters that control the DSA intensity and kinetics, like solute diffusivity, deformation activation energy/binding energy between solute atoms and arrested mobile dislocations, will be obtained by the intelligent microstructural and mechanical experimental investigations. The respective domain that limits the range of DSA/PLC effect in the UFG Al-Mg alloys (e.g. Al-1Mg and Al-5Mg) at the temperatures from RT to 300 °C and at the strain rates from 10-5s-1 to 10-3s-1 will be built on the basis of the theoretical model predictions and experimental results.