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

本研究的目的是：1)研究SDP工艺对超细Al-Mg合金DSA和PLC效应的影响；2)探讨DSA和PLC效应对SDP工艺超细Al-Mg合金变形行为的影响。在第一阶段进行的研究表明，外在SPD工艺对DSA和内在DSA效应对SPDed UFG Al-Mg合金在室温下的变形行为都有很大影响(见本申请第1节所列第一阶段的工作报告和与项目相关的出版物[1])。为了更深入地了解这些复杂的相互作用，必须在第二阶段进行基于实验结果的理论分析。为此，将使用最近开发的粗晶/小应变面心立方合金的DSA模型和非常大应变的面心立方金属和合金的应变硬化模型。然而，必须对它们进行修改，以考虑到显著细化的晶粒度，严重增加的位错密度，从而增强了固相沉积Al-Mg合金中的溶质扩散能力。模型修正所需的微观结构、力学和热力学数据将从实验结果中获得。因此，在第二阶段，实验研究将从RT扩展到高温(分别为50℃、100℃、200℃和300℃)。通过智能化的微观组织和力学实验研究，将获得超快凝Al-Mg合金在高温下的组织演变和力学行为的信息，以及控制DSA强度和动力学的热力学参数，如溶质扩散系数、形变激活能/原子间结合能和受阻移动位错。在理论模型预测和实验结果的基础上，建立了在RT~300℃和10~(-5)s~(-1)~10~(-3)s~(-1)应变速率下，超细Al-Mg合金(如Al-1 Mg和Al-5 mg)的DSA/PLC效应范围。

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.