【作者】 赵东山；

【导师】 沈宁福； 王仁卉；

【作者基本信息】 郑州大学 ， 材料加工工程， 2003， 博士

【摘要】 本文对Al-Cu-Fe系合金(成分范围Al_48-60Cu_33-50Fe_0-10的铸态及热处理态试样，采用金相（OM），X射线衍射（XRD），差热分析（DTA），扫描电子显微术（SEM）和透射电子显微术（TEM）等研究方法，对其显微组织、相结构及相组成等进行了分析。发现了Al-Cu-Fe合金中稳定的三元化合物Φ相具有两种变体：高温变体Φ₁和低温变体Φ₂。在873K以上，高温结构Φ₁具有τ₃（Al₃Cu₂）型结构，沿着＜111＞B₂有3倍的调制；低温结构Φ₂在763 K以下，具有沿着＜011＞B₂方向的10倍的调制结构。微区X射线能谱（EDXS）分析表明，Φ相化学成分范围为Al_47.3-50.6Cu_45.4-48.1Fe_4.5-5，成分区中心是Al_47.9Cu_47.1Fe_5.0。此外还发现了Al-Cu-Fe合金中ε₁相的结构。通过对照模拟计算的与实验的选区电子衍射（SAED）花样，对Al-Cu-Fe合金中的β相，τ₃相，ε₁相，η₂相分别进行了鉴定，并指出如何由选区电子衍射花样的特征来区别这些相。 本文工作表明，在Gayle等报道的Al-Cu-Fe三元系液相面投影图中，β相液相面应划分为Φ+β两个区域，本文确定了三元化合物Φ相液相面与邻近相液相面的交线，修正了Al-Cu-Fe合金的局部液相面投影图。本文探明了三元化合物Φ相在初生准晶相的凝固过程中所起的作用，发现了一新的包共晶反应点U₈（～1073 K）：L+β→IQC+Φ。修正的三元相变反应为：包共晶反应U₅：L+IQC→Φ+ω（原反应U₅：L+IQC→β+ω），包共晶反应U₆：L+ε→Φ+η（原反应U₆：L+ε→β+η），包共晶反应U₇：L+Φ→ω+η（原反应U₇：L+β→ω+η）。 对准晶I相及其晶体近似相R相，提出了相应的自由能计算模型及算法，从热力学上论证了准晶(Al_61.89Cu_25.61Fe_11.10)I相的高温稳定性；在低于T_r（938K）时，将形成其晶体近似相R相。对准晶I相及其晶体近似相R相，根据经典的形核理论，采用所提出的自由能计算模型，计算并比较了非均质形核方式下的准晶I相及其晶体近似相R相的形核功及形核率。计算结果表明，合金熔体中，从很小的过冷，直到准晶I相的平衡液相面温度（T_L=1130K）下150K的过冷范围，准晶I相的形核功在10ev以下，而准晶I相的晶体近似相R相的形核功则趋于“无限大”，表明R相的形核难以实现。对准晶I相及其晶体近似相R相的形核率计算表明，从小的过冷直到准晶I相平衡液相面温度（T_L=1130K）下150K的过冷范围，准晶I相都会首先形核，而其晶体近似相R相不具备从液相中初生形核的动力学条件。 采用简化的传热物理模型，模拟计算了初生准晶I相的体积分数，并与实验测定值进行了比较和分析.分析表明，平衡的初生准晶I相的最大体积分数决定于合金的化学成分和状态图特征.当采用缓冷和水淬法制备时，可获得较大体积分数的初生准晶I相. 本文工作得到河南省特种功能材料重点实验室资助项目（No.9926）及国家自然科学基金资助项目（19974030）的支持.更多还原

【Abstract】 A series of Al-Cu-Fe alloys with chemical composition of Al48-6oCu33.5oFeo-io was prepared and the phase constituents in these alloys quenched from various temperatures were identified by using optical microscopy (OM), X-ray diffraction (XRD), differential thermal analyses (DTA), scanning electron microscopy (SEM) with energy dispersive X-ray spectrometer (EDXS) and electron back scattered diffraction (EBSD), and transmission electron microscopy (TEM) including high resolution TEM (HRTEM). The present investigation revealed that the stable ternary Al-Cu-Fe O phase has two variants. The high temperature variant (designated as 甶 phase) is stable when temperature is higher than 873 K and has a structure of t3(Al3Cu2) phase, which is a 3 times modulation structure along a <111>2 direction. The low temperature variant (designated as ? phase) is stable when temperature is lower than 763 K and has a 10 times modulation structure along a <011>2 direction. EDXS revealed that the chemical composition of <P phase was in the range of AUy.3-50.eCu45.4-48.iFe4.5-5, and its center composition was AUv.9(^47.iFes.o. Besides, the structure model of 81 -A^Cus phase, which was unknown before, had been identified by selected area electron diffraction (SAED). Chemical compositions and crystalline structures of some phases in these Al-Cu-Fe alloys, including 13, r\2, ? phases, which are vacancy-ordered phases based on the B2 structure, have been studied by SEM and TEM. p, 13, t|2, and si phases in Al-Cu-Fe alloys were identified by comparing experimental and calculated SAED patterns. By analyzing the rules of the appearance of superreflections in SAED patterns along different zone axes of different phases, the method of differentiating these phases by their SAED patterns has been pointed out.Compared with the polythermal projection proposed by Gayle et al, a main amendment has been made to divide the previous /??region into J3+0 two regions. A new ternary reaction is the quasiperitectic at Ug: L+/??CZH-IQC. IQC represents icosahedral quasicrystal phase. The revised ternary reactions are at U5: L+IQC?-" (revised from U5: L+ IQC?0 + "), at U6: L+e?<P+r\ (revised from Ue: L+ e ?& + q ), and at U7: L+<Z>co + q (revised fromU?: L+ 3 ?co + n.).A thermodynamic model and the calculation method of the change of Gibbs free energy during the primary solidification of the IQC and its approximant crystal phase have been proposed. The thermodynamic analyses show that the IQC is stable at high temperature and solidifies as a primary stable phase when temperature is greater than 938 K. Under which, its approximant crystal phase emerges.By using a proposed thermodynamic model for the calculation of the change of Gibbs free energy during the primary solidification of the IQC and its approximant crystal phase, the nucleation energies and nucleation rates for the IQC and its approximant crystal phase were calculated according to the classic theory. Calculation reveals that the nucleation energy for IQC is below lOev, and for its approximant cryatal phase, the nucleation energy reaches to infinity when the undercooling is in the range of 0-150 K. As a result, the IQC will nucleate primarily when the temperature of the undercooled liquid alloy is in the range of 1130 K to 980 K.A simplified heat transfer model was used to calculate the volume fraction of the primary IQC, and calculation results were compared with the experimental measurements. While the maximum volume fraction of the primary IQC in the equilibrium state can be determined by the chemical composition of the alloy and the data of the phase diagram, the slow cooling and solidification of the alloy in a mould retained at certain temperature followed by subsequent quenching into water can provide a relatively large volume fraction of the primary IQC.This project were supported by the Foundation of the Key Laboratory for Special Functional Materials of Henan Province (Grant No.9926) and National Natural Science Foundation of China (Grant No. 19974030).更多还原