Microstructural characterization of Cu/Al composites and effect of cooling rate at the Cu/Al interfacial region

Cu/Al composites are of vital importance in industrial applications because of their numerous advantages. The influence of bonding temperature and cooling rate on the microstructure and morphology of Cu/Al composites was investigated in this paper. The interfacial morphology and constituent phases at the Cu/Al interface were analyzed by optical microscopy and field-emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy. The results indicate that effective Cu-Al bonding requires a higher bonding temperature to facilitate interdiffusion between the two metals. The microstructural characteristics are associated with various bonding temperatures, which impact the driving force of interdiffusion. It is observed that cooling rate exerts a significant influence on the morphology and amount of the intermetallic compounds at the interfacial region. Meanwhile, microhardness measurements show that hardness varies with the bonding temperature and rate of cooling.     

铝铜连接的感应钎焊工艺

为使钎焊技术进一步提高,采用Zn-Al钎料对Al与Cu进行了感应钎焊连接研究,利用扫描电镜、X射线衍射和室温压剪试验等分析手段对接头的微观组织和室温剪切强度进行实验。结果表明,利用Zn-Al钎料可以实现Al与Cu的连接;接头的界面结构为Al/Al基固溶体＋Al-Zn共晶组织＋CuAl2金属间化合物/（Cu,Zn）固溶体层/Cu;在电流为340 A、时间为9 s的钎焊条件下,接头的剪切强度在室温下达到128.5 MPa。     

Cu-Al异种材料的感应加热焊接及其工艺研究

利用感应加热原理,使用功率为0~60 kW且连续可调的高频感应加热设备,完成Cu-Al合金板材的焊接,研究焊接件的界面形貌、元素分布及界面物相分析.分析加热电流和加热时间对界面形貌和结合强度的影响.采用ZWICK-Z050电子万能材料试验机测试界面结合强度,采用扫描电子显微镜和偏光显微镜观察界面形貌,用X射线衍射仪进行物相分析.结果表明：界面中间化合物主要为Al₂Cu,Cu₉Al₄和CuAl相,其中Cu侧主要是Cu₉Al₄和CuAl相,Al侧主要是Al₂Cu相;随着加热电流的增大或加热时间的延长,Cu-Al界面结合层由不平整变为平整,且宽度逐渐增大,同时Cu-Al界面结合强度先增大后减小.感应加热焊接试样界面结合强度可达53 MPa,结合良好.     

Effect of continuous induction annealing on the microstructure and mechanical properties of copper-clad aluminum flat bars

Copper-clad aluminum (CCA) flat bars produced by the continuous casting–rolling process were subjected to continuous induction heating annealing (CIHA), and the effects of induction heating temperature and holding time on the microstructure, interface, and mechanical properties of the flat bars were investigated. The results showed that complete recrystallization of the copper sheath occurred under CIHA at 460°C for 5 s, 480°C for 3 s, or 500°C for 1 s and that the average grain size in the copper sheath was approximately 10.0 μm. In the case of specimens subjected to CIHA at 460–500°C for longer than 1 s, complete recrystallization occurred in the aluminum core. In the case of CIHA at 460–500°C for 1–5 s, a continuous interfacial layer with a thickness of 2.5–5.5 μm formed and the thickness mainly increased with increasing annealing temperature. After CIHA, the interfacial layer consisted primarily of a Cu₉Al₄ layer and a CuAl₂ layer; the average interface shear strength of the CCA flat bars treated by CIHA at 460–500°C for 1–5 s was 45–52 MPa. After full softening annealing, the hardness values of the copper sheath and the aluminum core were HV 65 and HV 24, respectively, and the hardness along the cross section of the CCA flat bar was uniform.     

铜/铝异步轧制复合带的界面反应与强化机制

采用同步和异步轧制复合工艺制备铜/铝复合带,研究退火过程中的界面反应和异步轧制工艺的强化机制.利用扫描电镜观察界面微观组织和拉伸断口形貌,通过线扫描和电子探针分析界面元素分布,采用XRD进行界面物相分析,通过剥离和拉伸实验研究复合带的力学性能.结果表明,经400℃保温1h后界面形成具有三个亚层的扩散层组织,各亚层内元素含量存在突变;铝剥离表面检测到大量铜元素,化合物相包括CuAl₂,Cu₉Al₄,CuAl和Cu₄Al,而铜剥离表面只检测到Cu₉Al₄和Cu₄Al;异步轧制工艺可以提高界面结合强度和复合带的拉伸性能,使界面层在拉伸断裂后破坏程度降低.     

Effect of sintering temperature on the microstructure and thermal conductivity of Al/diamond composites prepared by spark plasma sintering

Spark plasma sintering was used to fabricate Al/diamond composites. The effect of sintering temperature on the microstructure and thermal conductivity (TC) of the composites was investigated with the combination of experimental results and theoretical analysis. The composite sintered at 550℃ shows high relative density and strong interfacial bonding, whereas the composites sintered at lower (520℃) and higher (580–600℃) temperatures indicate no interfacial bonding and poor interfacial bonding, respectively. High relative density and strong interfacial bonding can maximize the thermal conductivity of Al/diamond composites, and taking both effects of particle shape and inhomogeneous interfacial thermal conductance into consideration can give a fairly good prediction of composites’ thermal conduction properties.     

铜铝冷轧复合薄带热处理工艺研究

利用金相显微镜和万能材料试验机,通过界面组织观察和力学性能测试,系统研究了铜/铝/铜冷轧复合薄带的热处理工艺,并讨论了热处理工艺参数对铜铝冷轧复合薄带界面组织和力学性能的影响规律.通过研究,得出如下结论:随退火温度升高或保温时间的延长,复合带强度降低,塑性增强;退火后复合带界面宽度为2～5μm,界面有脆性化合物CuAl2,CuAl和Cu9Al4生成;410℃退火,保温10 min时复合带综合性能最佳,为复合薄带的最佳热处理工艺.     

高性能铜铝复合排的制备及界面研究

采用固-液法浇注和铸轧工艺制备铝/铜复合材料.研究不同工艺对铜/铝复合排界面结合强度的影响,并对铜/铝复合排界面结构和复合机理进行分析.结果表明:当进行300°C×1h热处理时,所得复合排的结合强度最高,多次热循环后复合排界面结合强度有所增加.电子探针能谱扫描分析(EDS)和X射线衍射分析(XRD)表明铜/铝复合界面上生成金属间化合物Al2Cu,Al4Cu9和AlCu相,从而使得界面层硬度增大.采用该方法制备的铜/铝复合排,整体拉伸强度达98MPa,电阻率为0.021 6×10-6Ω.m.     

Cu/Al管气体火焰钎焊接头特征及热力学分析

通过计算Cu/Al管氧乙炔气体火焰钎焊条件下形成金属间化合物的各化学反应的熵变,对Cu/Al金属间化合物的形成及向CuAl2转化的趋势进行了化学热力学分析;结合XRD、SEM、EDS研究了Cu/Al管氧乙炔气体火焰钎焊接头组织与元素分布特征。结果表明,Cu/Al管氧乙炔气体火焰钎焊条件下,接头中脆性金属间化合物CuAl2由Cu、Al原子的直接结合和其他Cu/Al金属间化合物与Al原子的继续反应生成,其中CuAl自主转化趋势较强;热力学计算分析与接头XRD分析结果一致。钎焊接头可分为3个特征区域:靠近Al基体侧形成了宽度约30μm的α-Al与α-Al+CuAl2二元共晶区;钎缝中心偏Al基体一侧形成了宽度约150μm组织细密的多元共晶组织区;钎缝中靠近Cu基体宽度约120μm区域,Cu的大量扩散并与Al充分反应,形成了粗大珊瑚状CuAl2。     

Microstructure and properties of an Al-Ti-Cu-Si brazing alloy for SiC-metal joining

An Al-Ti-Cu-Si solid-liquid dual-phase alloy that exhibits good wettability and appropriate interfacial reaction with SiC at 500-600℃ was designed for SiC-metal joining. The microstructure, phases, differential thermal curves, and high-temperature wetting behavior of the alloy were analyzed using scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, and the sessile drop method. The experimental results show that the 76.5Al-8.5Ti-5Cu-10Si alloy is mainly composed of Al-Al₂Cu and Al-Si hypoeutectic low-melting-point microstructures (493-586℃) and the high-melting-point intermetallic compound AlTiSi (840℃). The contact angle, determined by high-temperature wetting experiments, is approximately 54°. Furthermore, the wetting interface is smooth and contains no obvious defects. Metallurgical bonding at the interface is attributable to the reaction between Al and Si in the alloy and ceramic, respectively. The formation of the brittle Al₄C₃ phase at the interface is suppressed by the addition of 10wt% Si to the alloy.     

Interfacial microstructure and mechanical properties of Ti-6Al-4V/Al7050 joints fabricated using the insert molding method

Ti-6Al-4V/Al7050 joints were fabricated by a method of insert molding and corresponding interfacial microstructure and mechanical properties were investigated. The interfacial thickness was sensitive to holding temperature during the first stage, and a good metallurgical bonding interface with a thickness of about 90 μm can be obtained at 750℃. X-ray diffraction, transmission electron microscopy, and thermodynamic analyses showed that the interface mainly contained intermetallic compound TiAl₃ and Al matrix. The joints featured good mechanical properties, i.e., shear strength of 154 MPa, tensile strength of 215 MPa, and compressive strength of 283 MPa, which are superior to those of joints fabricated by other methods. Coherent boundaries between Al/TiAl₃ and TiAl₃/Ti were confirmed to contribute to outstanding interfacial mechanical properties and also explained constant fracture occurrence in the Al matrix. Follow-up studies should focus on improving mechanical properties of the Al matrix by deformation and heat treatment.     

Preparation of activated ceria and its desulfurization performance

Activated ceria (CeO₂/γ-Al₂O₃) prepared by impregnation was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and hydrogen temperature-programmed reduction (TPR). The desulfurization of the activated ceria was investigated by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TG). The results showed that ceria could be highly dispersed or crystallized on the surface of γ-alumina. The reduction temperatures of 0.1CeO₂/γ-Al₂O₃, 0.45CeO₂/γ-Al₂O₃, and CeO₂ ranged from 250℃ to 470℃, 330℃ to 550℃, and 350℃ to 550℃, respectively. The reduction peak temperature of 0.45CeO₂/γ-Al₂O₃ was higher than that of 0.1CeO₂/γ-Al₂O₃, which was consistent with the reduction temperature of CeO₂. O₂ participated in the reaction between ceria and sulfur dioxide. The desulfurization product was cerium(Ⅲ) sulfate. The intensity of the hydroxyl band decreased with the formation of sulfate species.     

A novel diffusion model considering curvature radius at the bonding interface in a titanium/steel explosive clad plate

This article introduces an element diffusion behavior model for a titanium/steel explosive clad plate characterized by a typical curved interface during the heat-treatment process. A series of heat-treatment experiments were conducted in the temperature range from 750℃ to 950℃, and the effects of heat-treatment parameters on the microstructural evolution and diffusion behavior were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction analysis, and electron-probe microanalysis. Carbon atoms within the steel matrix were observed to diffuse toward the titanium matrix and to aggregate at the bonding interface at 850℃ or lower; in contrast, when the temperature exceeded 850℃, the mutual diffusion of Ti and Fe occurred, along with the diffusion of C atoms, resulting in the formation of Ti–Fe intermetallics (Fe₂Ti/FeTi). The diffusion distances of C, Ti, and Fe atoms increased with increasing heating temperature and/or holding time. On the basis of this diffusion behavior, a novel diffusion model was proposed. This model considers the effects of various factors, including the curvature radius of the curved interface, the diffusion coefficient, the heating temperature, and the holding time. The experimental results show good agreement with the calculated values. The proposed model could clearly provide a general prediction of the elements’ diffusion at both straight and curved interfaces.     

Au-Cu-Al合金相变的内耗

利用内耗方法分别对淬火态和时效态Au7Cu5Al4合金的相变过程进行了研究,分析了2种状态马氏体相变的差异.结果表明：淬火态与时效态Au7Cu5Al4合金的马氏体相变开始温度分别为-2.7和13.8 °C;根据驰豫内耗峰信息得出其晶界驰豫激活能分别为131.5和93.0 kJ/mol,反映了时效前后Au7Cu5Al4合金有序度的差异,即淬火态Au7Cu5Al4合金母相在室温下主要为B2结构,而时效态合金为L21有序结构.     

放电等离子烧结Al20Cr20Fe25Ni25Mn10高熵合金的硬度和腐蚀性能研究

采用放电等离子烧结(SPS)技术在不同温度（800、900和200°C）下保温不同时间（4、8和12 min）合成了Al₂₀Cr₂₀Fe₂₅Ni₂₅Mn₁₀高熵合金（HEA）。通过扫描电子显微镜、能谱仪（EDS）、维氏显微硬度计、极化曲线等对合金的微观结构、显微硬度和腐蚀进行了实验研究。X-射线衍射（XRD）表征了所制备合金的成分。EDS结果显示不论烧结参数如何变化,合金均由原始合金元素组成。XRD、EDS和扫描电子显微镜的结果说明所制备的合金具有球形微观结构,呈现出面心立方结构相,这是基于固溶机制形成的。这表明SPS合金具有HEAs的特征。在1000°C保温 12 min生产的合金显微硬度最高,为HV 447.97,热处理后其硬度降至HV 329.47。同一合金表现出优异的耐腐蚀性能。烧结温度升高,Al₂₀Cr₂₀Fe₂₅Ni₂₅Mn₁₀合金可具有更高的密度、显微硬度和耐腐蚀性。     

Ti6Al4V和Al2A12的扩散连接界面组织及力学性能

采用热等静压(HIP)工艺连接Al2A12和Ti6Al4V两种不同的航空航天用材料.利用扫描电镜、能谱仪和X射线衍射仪观察连接过渡区的微观组织和组成的演化,并测试其主要的力学性能.结果表明:采用热等静压制备这两种材料的界面连接好;Ti/Al反应层界面处形成了不同的金属间化合物,例如,Al3Ti、TiAl2和TiAl;连接接头处硬度为163HV,界面连接处剪切强度达到了23MPa,比只添加镀层而无中间层的连接强度提高了约17.9%,但低于带有中间层的连接强度.由于过烧和孔隙的形成使得断裂方式是脆性断裂.由此可知,在热等静压成形过程中异种材料的元素发生了相互扩散,在扩散连接处形成了不同的金属间化合物,这些金属间化合物影响连接处的力学性能.     

Experimental and numerical study on plasma nitriding of AISI P20 mold steel

In this study, plasma nitriding was used to fabricate a hard protective layer on AISI P20 steel, at three process temperatures (450°C, 500°C, and 550°C) and over a range of time periods (2.5, 5, 7.5, and 10 h), and at a fixed gas N₂:H₂ ratio of 75vol%:25vol%. The morphology of samples was studied using optical microscopy and scanning electron microscopy, and the formed phase of each sample was determined by X-ray diffraction. The elemental depth profile was measured by energy dispersive X-ray spectroscopy, wavelength dispersive spectroscopy, and glow dispersive spectroscopy. The hardness profile of the samples was identified, and the microhardness profile from the surface to the sample center was recorded. The results show that ε-nitride is the dominant species after carrying out plasma nitriding in all strategies and that the plasma nitriding process improves the hardness up to more than three times. It is found that as the time and temperature of the process increase, the hardness and hardness depth of the diffusion zone considerably increase. Furthermore, artificial neural networks were used to predict the effects of operational parameters on the mechanical properties of plastic mold steel. The plasma temperature, running time of imposition, and target distance to the sample surface were all used as network inputs; Vickers hardness measurements were given as the output of the model. The model accurately reproduced the experimental outcomes under different operational conditions; therefore, it can be used in the effective simulation of the plasma nitriding process in AISI P20 steel.     

Cu表面氧化规律及其对铜—陶瓷材料键合强度的影响

在用于电力半导体模块的新型封装材料ＣｕＡｌ２Ｏ３陶瓷直接键合基板中，Ｃｕ与Ａｌ２Ｏ３间形成的键合，是通过ＣｕＡｌＯ化学键，以Ｃｕ２Ｏ为中介形成的，其键合强度主要受ＣｕＣｕ２Ｏ之间的结合力限制．从而可以认为，铜箔表面的氧化层对键合强度起着极为重要的作用．为此，文中对Ｃｕ表面的氧化规律、氧化层厚度与时间和温度间的关系及其对ＤＣＢ板界面键合强度的影响进行了仔细的研究，获得了较理想的结果．     

Mg/Al异种材料瞬间液相过冷连接工艺研究

采用瞬间液相过冷连接工艺对AZ31镁合金和5083铝合金进行连接实验,研究保温扩散时间t2对焊缝微观组织及力学性能的影响。利用SEM,EDS,XRD和微观硬度计对接头剖面的微观组织和力学性能进行表征;在拉伸试验机上测试接头拉伸强度,利用SEM对断口形貌进行分析。研究结果表明:采用瞬间液相过冷连接工艺可以实现Mg/Al异种材料的有效连接;随着保温扩散时间t2的增加,接头的抗拉强度随之提高,当t2=30 min时,接头抗拉强度最高达到20.5 MPa;拉伸断口形貌具有明显的脆性断裂的特征,铝合金侧主要有解理面和撕裂棱组成,而镁合金侧属于典型的沿晶断裂形貌;在接头处形成MgAl,Mg2Al3,Mg0.44Al0.56和Mg17Al12金属间化合物,结合界面的微观维氏硬度最高达320。