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Al-Cu合金定向凝固固溶体中溶质浓度的影响因素研究
Study of the Factors Influencing the Solute Concentration in the Solid Solution of Directionally Solidified Al-4wt.%Cu Alloys
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- DOI:
- 作者:
- 帅三三
尹 莉,帅三三,胡 涛,陈超越,王 江,任忠鸣
- 作者单位:
- 上海大学 材料科学与工程学院,高品质特殊钢冶金与制备国家重点实验室
School of Materials Science and Engineering, State Key Laboratory of Advanced Special Steel, Shanghai University
- 关键词:
- Al-Cu合金;定向凝固;微观偏析;溶质分布;非平衡共晶
Al-Cu alloy; directional solidification; microsegregation; solute concentration; non-equilibrium eutectic
- 摘要:
- 本文以Al-4wt.%Cu亚共晶合金为研究对象,探究了合金凝固过程中溶质的分布规律和影响因素。使用扫描电镜(SEM)、能谱(EDS)等方法,研究了不同试样尺寸、初始变形量以及晶体取向条件下定向凝固单晶Al-4wt.%Cu合金微观组织形貌及固溶体内溶质浓度变化。结果表明:随着试样直径增大,Al-4wt.%Cu合金内非平衡共晶相体积分数提高,Cu溶质成分曲线越平缓,α-Al固溶体Cu溶质分布更加均匀,晶内偏析减小,这主要是由于大尺寸试样熔体中自然对流更加充分,促进了溶质在液相中的扩散,减轻了固液界面前沿溶质的富集;施加一定塑性变形后,由于变形导致试样中位错密度增加,位错增殖和运动过程中形成的空位缺陷可以容纳更多溶质原子,因而凝固初期Cu成分曲线升高,α-Al固溶体中溶质浓度增大;对于不同取向的试样,随着晶体取向偏离[001]方向角度增大,微观偏析先降低后增大,而固溶体中溶质浓度先增大后降低。分析表明由于固/液界面能各项异性存在,溶质原子进入固/液界面的难易程度与晶体取向相关,不同晶面上原子的吸附能力不一致,从而导致固液界面前沿溶质富集和固溶体中溶质浓度存在差异。
In this paper, the solute distribution and influencing factors in solidification of Al-4wt.% Cu hypoeutectic alloy were studied. The microstructure morphology and solute concentration in solid solution of directionally solidified single crystal Al-4wt%. Cu alloy with different sample sizes, initial deformation and crystal orientations were studied by means of SEM and EDS. The results indicated that the volume fraction of the non-equilibrium eutectic phase of Al-4wt.% Cu alloy increased with the increase of sample diameter. The Cu solute composition curve tended to flatten, the distribution of Cu solutes in α-Al solids tended to be uniform, and the microsegregation decreased. This is mainly due to the presence of sufficient natural convection in the large sample melt, which facilitated the diffusion of the solute in the liquid phase. Therefore, solute enrichment of the solid-liquid interface decreased. In addition, under a certain plastic deformation, the density of dislocation in the sample increases, and the vacancy defects formed during dislocation proliferation and movement can accommodate more solute atoms. During the initial solidification stage, the Cu composition curve and solute concentration in α-Al solid increased. For samples with different crystal orientations, when the angle of crystal orientation deviates from the [001] direction increased, the microsegregation decreased and then increased, while the solute concentration in solid solution changed in the inverse direction. The results showed that the anisotropy solid-liquid interface energy made the entry of the solute atom into the solid-liquid interface dependent on crystal orientation. The adsorption capacity of atoms on different crystal planes was different, which leaded to the discrepancy between the solute enrichment and the solute concentration before the solid-liquid interface.