C/Ti/Cu interfacial reaction in SiC<Subscript>f</Subscript>/Cu composites

Continuous SiC fiber reinforced copper matrix(SiCf/Cu) composites were prepared by fiber coating method,and Ti6Al4V interlayer was introduced as an interfacial modification coating to improve the interfacial bonding strength.The interfacial reaction characteristics were investigated by transmission electron microscopy(TEM).The results show that nearly all the titanium atoms reacted with the carbon coating of SiC fibers to form two layers of TiC.Also,a thin copper layer that is sandwiched between these two layers was detected.No Ti-Cu interfacial reaction product was observed.The formation process of the interfacial reaction along with its mechanism was discussed.     

Glass forming ability and crystallization of Zr-Cu-Ag-Al-Be bulk metallic glasses

The glass forming ability of Zr₄₆Cu_37.64−xAg_8.36Al₈Be_x (x = 0, 6 and 10 at.%) bulk metallic glasses (BMGs) were significantly improved by Be addition. The critical size of amorphous rods can be over 35 mm diameter. The high GFA achieved is mainly due to the decrease of melting point and liquidus temperature, and suppression of the formation of crystalline phases during solidification from liquid state. The high stabilization with supercooled liquid regime of 115 K was found for the BMG with x = 10 at.%. Two independent exothermic events happen in x = 0 and 6 at.% BMGs, corresponding to the formation of primary crystalline phases Cu₁₀Zr₇ and AgZr, then transforming to final stable crystalline phases Zr₂Cu and AlCu₂Zr. However, in the x = 10 at.% BMG, the precipitation of primary phases and transformation to final stable phases are within the first exothermic event and the AlCu₂Zr phase is totally suppressed.     

Ce基催化剂对2LiBH4/MgH2放氢性能的影响

采用球磨方法制备了2LiBH4/MgH2复合储氢材料体系,用XRD、FTIR和储氢性能测试手段等对复合体系结构和储氢性能进行表征,研究了不同Ce基催化剂对复合体系放氢性能的影响,分析了催化剂的催化机理。结果表明:2LiBH4/MgH2复合物加热过程为明显的两步放氢,第1步主要发生MgH2的分解放氢;第2步为第1步生成的Mg与LiBH4发生放氢反应;添加Ce和CeF3都能提高2LiBH4/MgH2体系的放氢性能。Ce主要改善体系第2步放氢特性,CeF3对体系两步放氢反应均产生显著效果。添加5mol%CeF3使2LiBH4/MgH2体系起始放氢温度降低约100℃,体系最大放氢量达到10.6%(质量分数,下同);F-取代部分H-形成LiBH1-xFx,改善了LiBH4的分解特性,从而显著改善了2LiBH4/MgH2体系的放氢性能。     

Influence of resistance heating on self-piercing riveted dissimilar joints of AA6061-T6 and galvanized DP590

The hybrid use of aluminum alloy and advanced high strength steel (AHSS) has become an inevitable trend for fabricating a lightweight auto-body. Self-piercing riveting (SPR) as a preferred cold-forming fastening method is facing problem like weak interlocking when joining dissimilar combinations with considerably unequal thickness. In this study, a hybrid joining method, named rivet-welding (RW) was proposed to improve the robustness and strength of the SPR joint, by applying an electric current to it. For better evaluating the new process, the effects of heating time and electrode design on the microstructure, micro-hardness distribution, and mechanical performance of the RW joints were studied and compared systematically with the traditional SPR ones. The results showed that the electric current could improve the microstructure of the steel rivet and bottom DP590, and under long heating time, the inter-metallic compounds (IMC) could be formed at the interface of trapped AA6061-T6 and bottom DP590. Meanwhile, the electric current could increase the micro-hardness of the rivet and bottom DP590, and soften the AA6061-T6 around the rivet leg. In addition, the RW process using lower annular electrode A (LAE_A) could obtain 12.1% higher tensile-shear strength compared with the traditional SPR process.     

Study on Microstructure of 6061 Aluminum Alloy Brazed with Al-Si-Zn Filler Metals Bearing Sr and Ti

制备了Sr及Ti变质的Al-Si-Zn钎料,并将其应用于6061铝合金的钎焊,研究Sr及Ti对Al-Si-Zn钎料6061铝合金钎焊性能的影响。结果表明：锌的加入使得钎料熔点由铝硅共晶温度下降至520 ℃左右。添加少量改性元素Sr及细化晶粒元素Ti,极大优化了钎料中Al-Si共晶的形态与分布,同时也细化了钎料中的α-Al固溶体。向钎料中添加0.08%Ti元素,使得原来Al-Si-Zn-Sr-0.04Ti钎料钎缝中大块团簇状的铝硅共晶均匀分布于α-Al固溶体之间。在6061铝合金钎的焊界面处可以发现较为明显的过渡层,由于钎焊过程中母材元素发生了向钎料中扩散,母材中的锰元素与钎料中的铁杂质生成块状锰铁相避免了针状β-Fe的生成     

Improving Corrosion Resistance of Ferrous Alloy to Molten Zn by Modifying the Laves Phase Characteristics

The Laves phase morphology in the Fe25Mo14Cr10Ni1Si (wt.%) alloy was modified by Si addition to improve the corrosion resistance of the ferrous alloy to molten zinc. The Si-containing alloy showed a woven, needle-like Laves phase with higher Mo content than that of the Fe25Mo14Cr10Ni alloy. Corrosion resistance to molten Zn for the Si-containing alloy was more than 20 times higher than that of the silicon-free alloy mainly as a result of the characteristics of the modified Laves phase. This phase was oriented perpendicular to the Zn-diffusion direction, which effectively prevented corrosion by the molten Zn, leading to a denser FeZn₁₃ layer rather than the FeZn₁₀ layer produced in the Fe25Mo14Cr10Ni alloy.     

离子色谱法快速分析牙膏中多种阴离子含量

研究了一种有效测定牙膏中7种阴离子含量的方法.提出用亚沸水作提取剂、手动振荡后经离心分离、膜过滤和过RP柱的前处理方法.结果表明,该方法检出限为2.8～29.6 μg/L,相关系数为0.997 9～0.999 9,标准偏差(RSD)为0.33%～2.84%,加标回收率为98.6%～101.2%.并研究了提取剂对分析结果的影响及乙醇溶液对测定结果的干扰.对比氟离子选择电极法与离子色谱法对氟化物牙膏样品测定,其结果基本吻合,证明该方法准确可靠.     

三维激光扫描技术在立体织物检测中的应用

分析了近年来随着航空、航天技术的迅猛发展,对复合材料提出了更高的要求,作为增强体的立体织物也向大尺寸、复杂形面一体化成型发展,产品的近净尺寸仿形成型对检测的要求也逐步提升,传统的检测法已无法满足要求的现状.提出了1种三维激光扫描无接触检测法.通过检测应用,证明了检测立体织物尺寸和复杂形面仿形程度的可行性,并具有较高的检测精度.     

稀土对原位TiCp/Fe复合材料微观结构的影响

研究了稀土元素加入后原位TiCp/Fe复合材料微观结构的变化，结果表明：稀土元素在Fe-Ti-C熔体中可形成细小的稀土复合化合物粒子，能促进TiC增强体的非均匀形核，并使组织中原位TiC颗粒的尺寸增加，数量减少，与此同时，添加稀土元素有效地改善了组织中Fe2Ti相的分布，晶界上已无明显的Fe2Ti相存在，有利于材料性能的改善。     

A Molecular-Level Interface Design Enabled High-Strength and High-Toughness Carbon Nanotube Buckypaper

Buckypaper (BP) assembled by carbon nanotubes (CNTs) is considered as a promising macroscopic material with excellent multifunctional properties. However, the poor interfacial stress-transfer ability between CNTs seriously limits its further applications. This paper proposes a novel approach to simultaneously improve both the tensile strength and the toughness of BPs, where a commercial poly(amido amine) (PAMAM) dendrimer is utilized to serve as an interfacial bridging agent, by realizing effective chemical cross-linking between CNTs. The result shows that the introduction of PAMAM can increase the tensile strength, Young's modulus, and toughness by 306%, 168%, 1007%, respectively, compared with that of pristine BPs based on weak van der Waals interactions. In addition, molecular dynamics (MD) simulation is employed to reveal the proposed interfacial enhancement. It is found that the elastic deformation, uncoiling, interlocking of PAMAM dendrimers, and chemical bonds between PAMAM dendrimers and CNTs contribute to the improvement of the macroscopic strength and toughness of BPs. More importantly, it is found that the formed amido bonds are very strong, and the breakage of chemical bonds occurs at C─N bonds within PAMAM themselves. This work provides a new route for interfacial structure design and an in-depth understanding of mechanical properties of BPs.