一种研究Cu/Al界面原子扩散Kirkendall效应的新方法

利用铆钉法制备了Cu—Al扩散偶。借助光学显微镜和彩色金相技术，通过分析烧结过程中销钉及销孔直径尺寸的变化，研究了Cu／Al界面原子扩散的Kirkandall效应。结果表明，在烧结温度范围内铜向铝中的扩散强度大于铝向铜中的扩散强度。     

组元配比对球磨固态燃烧式反应和扩散型反应的影响

采用搅拌式高能球磨机研究了不同铝含量的Al/CuO球磨固态燃烧反应和Al-Cu及Al-Cu-Al2O3扩散型反应。结果表明：理想配比的Al/CuO的反应孕育期最短,偏离这一配比,孕育期延长,反应由整体燃烧式逐渐过渡到渐进燃烧式完成;球磨强度扩大以燃烧式进行的组元配比范围;当铝含量超过理想配比中的比例,随Al含量增加,反应由单一的还原反应向还原＋合成复合反应模式转化,反应产物为平衡组织,依次为Cu Al2O3、CuoAl4 Al2O3、CuAl2 Al2O3、Al(Cu) Al2O3;而球磨Al-Cu和Al-Cu-Al2O3体系的反应以扩散方式进行,产物是非平衡组织。     

Al-Fe液/固复合界面扩散溶解层研究

采用镶嵌式扩散偶技术制备了Al-Fe扩散偶,在Al熔点以上Fe熔点以下进行扩散热处理,研究了Al-Fe液/固界面扩散溶解层的组织结构演变、形成机理及生长规律。实验结果表明,Al-Fe扩散偶扩散热处理后的组织结构为Al+FeAl3/FeAl3/Fe2Al5/Fe;Fe2Al5层是保温过程中第一个出现的也是唯一出现的连续单相层,FeAl3层则是在冷却过程中形成;Al基中存在针状的和条状的FeAl3析出相,从界面附近到远离界面,析出相的密集程度和尺寸都逐渐小;在相同的保温时间下,热处理温度与扩散溶解层厚度之间存在指数关系;在相同的热处理温度下,保温时间与扩散溶解层厚度偏离抛物线关系。     

Cu/Zn扩散偶的实验研究

用铆钉法将块体铜和块体锌制成Cu／Zn扩散偶，经真空炉扩散处理后，在扩散偶Cu／Zn界面处形成一个既不同于铜也不同于锌的扩散层。实验表明，除扩散温度和时间对扩散层有影响外，扩散偶的几何尺寸对扩散层的形成也有影响。扩散偶中锌销子的直径越小，形成扩散溶解层的速度越快，扩散厚度越大。     

Fe_2O_3/TiO_2扩散偶的固相反应

采用扩散偶的方法研究了Fe2O3和TiO2在1373K空气气氛不同时间下的固相反应。采用场发射扫描电镜对扩散偶表面形貌进行观察和线扫描能谱分析。根据线扫描能谱分析所得的组元扩散浓度曲线,用Den Broeder改进的Boltzmann-Matano法计算出Fe2O3/TiO2扩散偶的互扩散系数,结果发现互扩散系数与Fe3+浓度呈一定的线性关系,并随着Fe浓度的升高而增大,同时用空位扩散机理讨论了Fe2TiO5的形成。     

电场作用下AZ31B/Cu扩散界面的结构及性能

采用电场激活扩散连接技术(FADB)实现了AZ31B/Cu的扩散连接.利用SEM、EDS和TEM分析了扩散溶解层的显微组织、相组成和界面元素分布.采用万能试验机对连接界面的抗剪切性能进行了测试.结果表明:AZ31B与Cu通过固相扩散形成了良好的冶金结合界面,扩散温度低于475℃时扩散溶解层由MgCu2、Mg2Cu和MgCuAl组成,此时接头的薄弱环节为Mg2Cu.扩散温度为500℃时扩散溶解层由Mg2Cu、(α-Mg+ Mg2Cu)共晶组织和MgCuAl组成,共晶组织的形成导致接头的抗剪强度进一步降低,并成为新的薄弱环节.当扩散温度为450℃,保温时间为30min时,界面的抗剪强度随保温时间的延长先增大后减小,最大可达40.23MPa.     

Ti/Cu扩散溶解层的组织结构和形成规律

采用镶嵌式扩散偶,在不同退火处理条件下,对Ti/Cu扩散溶解层进行了研究.利用扫描电子显微镜和电子探针显微分析仪观察和分析了扩散溶解层的组织结构和形成规律.结果表明,随着加热温度的升高和保温时间的延长,在Ti/Cu界面处会形成相界面依附于扩散偶组元Cu丝、形态各不相同、层数以及总层与单层厚度逐渐增加的"环状"扩散溶解层;当进行700℃、100小时真空退火热处理时,扩散溶解层厚度为93μm;其中一层呈"锯齿状"朝向Cu,分别有两层处于同一个层区域内,并以"竹笋状"方式互相交错重叠;结构为Cu/Cu4Ti/Cu2Ti/Cu3Ti2/Cu4Ti3/CuTi/CuTi2/Ti,而且其结构与Cu-Ti相图上各个相的左右排列顺序一致.不同的扩散温度和时间,Ti/Cu相界面处将几乎同时结晶出不同层数、厚度和结构的扩散溶解层.     

镁含量和硅对铁-锌铝镁合金固-液扩散偶中Fe-Al反应层的影响

在热浸镀锌中,铁基表面Fe-Al化合物层的形成会影响镀层的生长和质量。将Fe/(Zn-11%Al-3%Mg)和Fe/(Zn-11%Al-x%Mg-0.2%Si)扩散偶在600℃下进行25min的固-液扩散实验,利用扫描电子显微镜(SEM)和能谱仪(EDS)研究了镁含量和硅对铁-锌铝镁合金固-液界面Fe-Al合金层形成的影响。结果表明,Fe/(Zn-11%Al-3%Mg)固-液扩散偶反应层由FeAl3和Fe2Al5相层组成;随着Mg含量的增加,Fe/(Zn-11%Al-x%Mg-0.2%Si)扩散偶中反应层的厚度呈现先增加后减少再增加的变化趋势,当镁含量为3%时反应层厚度最薄;Fe/(Zn-11%Al-3%Mg)扩散偶中Fe-Al反应层的平均厚度比Fe/(Zn-11%Al-3%Mg-0.2%Si)扩散偶中反应层的厚度大60μm,证明Si元素起到抑制Fe-Al反应层形成的作用。研究结果为解释Super Dyma合金镀层中不形成明显的Fe-Al抑制层提供了实验依据。     

近熔态扩散新工艺制备SiC纤维增强Al基复合材料的界面分析

采用近熔态扩散新工艺制备了SiCf /Al(5A02)铝合金基复合材料,采用透射电镜(TEM)和X射线能谱 (EDX)分析了界面产物和反应机理.与采用传统固态扩散法制备的样品相对比,样品界面处没有形成脆性相Al4C3,且Al2O3被MgO取代;而固态扩散工艺制得的样品界面处发现针状或块状的Al4C3在C涂层或附着在C涂层上的Al2O3边缘形成,并向基体中生长,破坏了界面的连续性.采用近熔态扩散法制备的样品由于合金元素Mg在从半液态冷却过程中偏聚到界面附近,并与Al2O3发生反应,生成细小的MgO颗粒,阻碍了C的扩散,并抑制了脆性相Al4C3的形成,有利于对界面有害反应的控制.     

Al/Fe液-固界面扩散反应层生长动力学分析

采用镶嵌式技术制备了Al/Fe扩散偶,在铝熔点以上铁熔点以下进行扩散热处理,对Al/Fe液-固界面扩散反应层的生长动力学进行了分析,并建立了生长动力学方程。结果表明,Fe2Al5是热处理保温过程中唯一生成的新生相。在Fe2Al5连续单相层形成之前,其生长受Al原子和Fe原子的化学反应控制;一旦连续的Fe2Al5单相层形成,其生长则主要依赖于Al原子沿其晶界的扩散控制,且伴随着其晶粒尺寸的长大。在800℃以下热处理,可忽略晶粒长大对原子扩散的影响,其生长动力学方程为:y=2020.96exp(-78490/RT)t0.25。但当热处理温度超过铁熔点的0.7倍后,则不能忽略晶粒长大的影响,应适当减小生长动力学方程中的生长指数值。     

Effect of Precipitating Phases on Tensile Strength and Microstructural Stability of a Spray-Deposited Al-Si-Fe-Mn-Cu-Mg Alloy

Spray deposition is a novel process which is used to manufacture rapidly solidified bulk and near-net-shape preforms. In this study, AI-20Si-5Fe-3Mn-3Cu-1Mg alloy was synthesized by spray deposition technique. The aging process of the alloy was investigated by differential scanning calorimetry (DSC) analysis and transmission electron microscopy (TEM). The results show that two kinds of phases, i.e. S(Al2CuMg) and σ(Al5Cu6Mg2), precipitate from matrix and improve the tensile strength of the alloy efficiently at both the ambient and elevated temperatures (300℃). In addition, the σ-Al5Cu6Mg2 is a relatively stable phase which improves microstructural stability of the alloy.     

Effect of silver addition on formation of secondary phases in squeeze cast Al–Cu–Mg alloys

Abstract

The effect of silver addition on the formation of secondary phases in squeeze cast Al–4.0Cu–1.5Mg and Al–4.0Cu–1.5Mg–0.7Ag (all wt-%) alloys has been investigated using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffractometry, and transmission electron microscopy. The as cast microstructure of both alloys consists of primary dendritic α-Al and various types of secondary solidification phase, e.g. Al₂Cu, Al₂CuMg, Al(Cu,Ag)Mg, and icosahedral (I) and decagonal (D) quasicrystalline phases. However, the solidification path in the interdendritic region during squeeze casting is different for each alloy, i.e. L→ternary α-Al–Al₂Cu–Al₂CuMg eutectic in Al–4.0Cu–1.5Mg and L→L′+Al₂Cu→α-Al–Al₂Cu–Al(Cu_0.75Ag_0.25)Mg eutectic in Al–4.0Cu–1.5Mg–0.7Ag. This indicates that silver acts as an alloying element stabilising the formation of Al(Cu,Ag)Mg Laves phase. The remaining copper and iron rich liquid in the interdendritic region at the final stage of solidification solidifies into a mixed structure of α-Al, Al₂Cu, and AlCuFe I (or D) phases. The composition of the I and D phases, measured by energy dispersive X-ray spectroscopy, is in the range Al–(27～28)Cu–(9～10)Fe and Al–(26～27)Cu–(7～9)Fe (all at.-%) respectively.     

Effect of Homogenization Process on Microstructure of Al–Zn–Mg–Cu Aluminum Alloys

Herein, the best homogenization process of 466.5 °C × 36 h + 490 °C × (14–26.4 h) that can completely eliminate the coarse phases σ[Mg(Zn, Al, Cu)₂] and S(Al₂CuMg) in the Al–Zn–Mg–Cu aluminum alloy is developed. The homogenization process is determined by the method of calculation phase diagram, and the experimental verification. It is shown in the results that, first, in the microstructure of the as-cast alloys, the crystal structure of the σ[Mg(Zn, Al, Cu)₂], Al₇Cu₂Fe, and Mg₂Si phases is determined. Second, during the homogenization process, the σ[Mg(Zn, Al, Cu)₂] phase dissolves and also transforms into the S(Al₂CuMg) phase. Most importantly, the dissolution temperature range of the σ[Mg(Zn, Al, Cu)₂], S(Al₂CuMg), and Al₇Cu₂Fe phases is determined from 472.56 to 476.36 °C, from 484.09 to 485.39 °C, and from 540.18 to 547.23 °C, respectively. At best homogenization process, the residual Al₇Cu₂Fe phase area fraction ranges from 1.28 ± 0.16% to 1.60 ± 0.18%. In addition, dispersed η(MgZn₂) phase precipitates in supersaturated Al-matrix during differential scanning calorimeter heating. And, the concentration differences between the grain center and the eutectic of structure of Zn, Mg and Cu regression equations are established, which can provide some reference for the design of experimental parameters, thus reducing the experimental workload.     

原位内生Al/M g2Si/S i 复合材料铸态组织研究

利用普通重力铸造方法, 制备了原位内生A l/Mg₂Si/S i 复合材料。研究了体系中加入过量Si 后的显微组织, 并利用Al-Mg₂Si-Si 三元相图进行分析。结果表明, 过量Si 使复合材料中的大长径比的Al+ Mg₂Si 二元共晶向小长径比的Al+ Mg₂Si+ Si 三元共晶转化, 并使α-Al 以球状晶粒析出, 从而改善了显微组织, 显著提高了复合材料的室温拉伸性能。      

Microstructure and precipitation in Al–Li–Cu–Mg–(Mn,Zr) alloys

Abstract

Hot rolled Al–6Li–1Cu–1Mg–0·2Mn (at.-%) (Al–1·6Li–2·2Cu–0·9Mg–0·4Mn, wt-%) and Al–6Li–1Cu–1Mg–0·03Zr (at.-%) (Al–1·6Li–2·3Cu–1Mg–0·1Zr, wt-%) alloys developed for age forming were studied by tensile testing, electron backscatter diffraction (EBSD), three-dimensional atom probe (3DAP), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). For both alloys, DSC analysis shows that ageing at 150°C leads initially to formation of zones/clusters, which are later gradually replaced by S phase. On ageing at 190°C, S phase formation is completed within 12 h. The precipitates identified by 3DAP and TEM can be classified into (a) Li rich clusters containing Cu and Mg, (b) a plate shaped metastable precipitate (similar to GPB2 zones/S″), (c) S phase and (d) δ′ spherical particles rich in Li. The Zr containing alloy also contains β′ (Al₃Zr) precipitates and composite β′/δ′ particles. The β′ precipitates reduce recrystallisation and grain growth leading to fine grains and subgrains.     

热变形方式对2D70耐热铝合金组织与性能的影响

分别采用常规变形方式(直接挤压)、强变形方式(3次多方锻造与挤压变形相结合)制备了大规格2D70耐热铝合金棒材,利用金相显微镜、透射电镜、力学性能测试、电导率测试等手段对比分析了两种工艺所获得棒材的变形态、固溶态显微组织特征以及195℃人工时效强化特性差异。结果表明,与传统直接挤压方式相比,采用强变形工艺所获得的基体组织相对均匀,合金中各类第二相破碎严重、分布合理;经强变形破碎的Al2CuMg、Al2Cu等可溶第二相可在固溶处理过程中充分回溶以提高时效强化潜力,同时,Al9FeNi、Al7Cu4Ni等难溶第二相的尺寸、形态与分布通过强变形得以合理调控,使得合金棒材在195℃人工时效的过时效阶段具有更优越的抗过时效能力,合金热稳定性较好。     

7050铝合金第二相溶解行为EI北大核心CSCD

研究热轧态7050铝合金在固溶过程中的平衡态η(MgZn2)相、T(Al2Mg3Zn3)相、S(Al2CuMg)相及含铁Al7Cu2Fe难溶相的溶解行为。采用原位扫描的组织检测方法获得上述平衡相的溶解动力学实测数据。在体扩散控制的溶解动力学模型基础上,引入曲率和界面反应对原子迁移速率的作用,建立η,T和S相溶解动力学模型。结果表明:在7050铝合金常规固溶温度(470℃)条件下,η和T相在2 min内即可完全溶解,S相保温较长的时间才能完全溶解,含Fe相不发生溶解;曲率对溶解行为影响较小,界面反应会大幅度降低溶解速率;本工作建立的η,T和S等第二相溶解动力学模型预测结果与实测结果吻合,能够为优化Al-Zn-Mg-Cu合金固溶工艺提供指导作用。     

超音气体雾化Al-Si合金粉末表面氧化和吸附特性

利用超音速气体雾化法制备Al-17Si-6Fe-4.5Cu-0.5Mg合金粉末，借助X射线光电子能谱（XPS）对粉要态合金表面氧化和吸附特性进行了研究，并对粉末表面层结构进行了分析。结果表明：粉末表面氧化主要以Al和Mg元素的氧化为主，氧化层成分主要为Al2O3，Al(OH)3和MgO，而合金中的Si,Fe及Cu元素很少氧化。除此之外，在粉末表面化还吸附一层含Cl元素的碳氢有机化合物污染层，测定表明粉末表面氧化层和吸附层总厚度约为2nm。     

Characterization of 2024-T3: An aerospace aluminum alloy

The 2024-T3 aerospace aluminum alloy, reported in this investigation, was acquired from a local aerospace industry: Royal Malaysian Air Force (RMAF). The heat treatable 2024-T3 aluminum alloy has been characterized by use of modern metallographic and material characterization techniques (e.g. EPMA, SEM). The microstructural characterization of the metallographic specimen involved use of an optical microscope linked with a computerized imaging system using MSQ software. The use of EPMA and electron microprobe elemental maps enabled us to detect three types of inclusions: Al–Cu, Al–Cu–Fe–Mn, and Al–Cu–Fe–Si–Mn enriched regions. In particular, the presence of Al₂CuMg (S-phase) and the CuAl₂ (θ′) phases indicated precipitation strengthening in the aluminum alloy.     

Cu/Al_2O_3复合薄膜的制备及其抗氧化性能

本文在纺织纤维基材表面采用二次溅射沉积法制备了Cu/Al_2O_3复合薄膜,利用扫描电镜(SEM)、X射线能谱仪(EDX)和矢量网络分析仪对室温环境下存放3600h的复合薄膜的表面形貌、元素含量以及屏蔽效能进行了测试,并与相同工艺条件下制备的纯Cu薄膜进行了对比分析。结果表明:与纯Cu薄膜结构的不稳定性相比,由于复合薄膜表层Al_2O_3薄膜的结构稳定性和致密性,Cu/Al_2O_3复合薄膜在保证高屏蔽性能的前提下,具有整体结构的稳定性,表现出了良好的抗氧化性能。