Improvement of Thermal Stability and Evaluation of Fatigue Behavior of an Ultra fine-Grained Al-Mg-Sc Alloy Using ECAE

利用 ECAE 提高超细晶 Al-Mg-Sc 合金的热稳定性并评估疲劳行为

基本信息

批准号：
14550652
负责人：
MONZEN Ryoichi
金额：
$ 1.73万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550652/
关键词：
Al-Mg-Sc alloy ECAE thermal stability ultra fine grain fatigue behavior dislocation structure coherent Al_3Sc precipitate particle

项目摘要

The microstructure evolution of an ultrafine grained Al-3wt%Mg-0.2wt% Sc alloy produced by equal channel angular pressing during annealing at 573 K or 623 K has been examined. Annealing at 623 K for a short time caused complete recrystallization of the ultrafine grains. The structure development at 573K can be divided into three stages as follows :(1)Initial stage (〜30min). The hardness decreases rapidly with annealing time and the grain size increases from 300 to 600 nm. The dislocation, density becomes lower by recovery, The grain growth and the reduction in dislocation density bring about the decrease in hardness.(2)Intermediate stage (30min〜11h). The hardness increases and the grain size remains almost unchanged. Fine precipitated Al_3Sc particles are formed in grain interiors. These particles cause primarily the increase of the hardness. The small Al_3Sc particles on grain boundaries pin grain boundaries and restrict their migration.(3)Later stage (11h〜). At this stage, again the … More grain growth occurs and the hardness decreases. This is because the pining force and the particle strengthening gradually decrease with increasing the Al_3Sc particle size. From the linear relationship between the grain size and Al_3Sc particle radius, it is concluded that the grain growth is controlled by the rate of coarsening of the Al3Sc particles.Plastic-strain-controlled low-cycle fatigue tests of an Al-Mg-Sc alloy containing Al_3Sc particles with average diameters 4 nm and 11nm were carried out. The results and conclusions are summarized as follows :(1)Specimens with Al_3Sc particles of 4nm in diameter show cyclic softening at higher plastic-strain amplitudes (ε_<pl>【greater than or equal】1×10^<-3>). All other specimens show cyclic hardening to saturation.(2)Dislocations were very uniformly distributed in specimens with Al_3Sc particle of 11nm in diameter. At higher strain amplitudes, the slip bands were observed in specimens with Al_3Sc particles of 4nm in diameter.(3)The fatigue softening of specimens with 4 nm Al_3Sc particles is unambiguously related to the dissolution of the Al_3Sc particles within the slip bands. Less

研究了在 573 K 或 623 K 退火过程中通过等通道角压制生产的超细晶粒 Al-3wt%Mg-0.2wt% Sc 合金的微观结构演变。在 623 K 下短时间退火导致超细晶完全再结晶。 573K时晶粒的结构发展可分为以下三个阶段：(1)初始阶段(〜30min)。随着退火时间的延长，硬度迅速下降，晶粒尺寸从300 nm增大到600 nm，位错、密度通过恢复而变低，晶粒长大和位错密度的降低导致硬度下降。(2)中间阶段(30min)。 ~11h)。硬度增加，晶粒尺寸几乎保持不变。这些颗粒是导致硬度增加的主要原因。晶界上的Al_3Sc颗粒钉住晶界并限制其迁移。(3)后期(11h〜)。此阶段再次发生晶粒长大，硬度逐渐降低。随着Al_3Sc颗粒尺寸的增加，晶粒尺寸与Al_3Sc颗粒半径之间的线性关系表明，晶粒长大受Al3Sc颗粒粗化速率的控制。塑性应变控制。对平均直径为4 nm和11 nm的Al_3Sc颗粒的Al-Mg-Sc合金进行了低周疲劳试验，结果和结论如下：(1)平均直径为4 nm的Al_3Sc颗粒试件出现循环软化。在较高的塑性应变幅度（ε_<pl>【大于或等于】1×10^<-3>）下，所有其他样本均表现出循环硬化。 (2)直径为11nm的Al_3Sc颗粒试样中位错分布非常均匀。在较高应变幅值下,直径为4nm的Al_3Sc颗粒试样中出现滑移带。(3)4nm试样的疲劳软化。 nm Al_3Sc 颗粒与滑带内 Al_3Sc 颗粒的溶解明显相关。