高合金化Al-9Zn-2Mg-2Cu-0.3Ce合金均匀化过程中的组织演变

采用光学显微镜(OM)、扫描电镜(SEM)、电子探针显微分析(EPMA)、X射线衍射(XRD)以及差示扫描量热仪(DSC),研究了一种高合金化Al-9Zn-2.0Mg-2Cu-0.3Ce(质量分数,%)合金的铸态微观组织,以及其均匀化过程中微观组织的演变,获得了较优的单级均匀化工艺。结果表明:铸态时,合金晶粒内部枝晶网络发达,Zn、Mg、Cu元素偏聚严重,合金中主要的非平衡凝固相为T(AlZnMgCu) 相和θ(Al₂Cu)相。经过470 ℃×48 h均匀化热处理后,合金中的枝晶网络基本消除,凝固相T逐渐回溶至基体中,主要的残留相为耐高温相Al₂CuMg、Al₈Cu₄Ce和Al₇Cu₂Fe。扩散动力学分析表明,470 ℃退火48 h的单级均匀化工艺足以使合金中的非平衡相回溶至基体中。

Microstructure evolution of a high alloying Al-9Zn-2Mg-2Cu-0.3Ce alloy during homogenization

As-cast microstructure and microstructure evolution during homogenization of highly alloying Al-9Zn-2.0Mg-2Cu-0.3Ce alloy were studied by means of optical microscope (OM), scanning electron microscope (SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD) and differential scanning calorimeter (DSC), and a rather optimal single-stage homogenization process was obtained. The results show that in the as-cast alloy, the dendrite network is well developed with serious segregations of Zn, Mg and Cu, and the main non-equilibrium solidification phases are T(AlZnMgCu) phase and θ(Al₂Cu) phase. After homogenization heat treatment at 470 ℃ for 48 h, the dendrite network in the alloy is basically eliminated and the solidification phase T gradually dissolves into the matrix. The main residual phases are high temperature resistant phases Al₂CuMg, Al₈Cu₄Ce and Al₇Cu₂Fe. Diffusion kinetic analysis shows that the single-stage homogenization process of annealing at 470 ℃ for 48 h is sufficient to make the non-equilibrium phase in the alloy to re-dissolve into the matrix.