异种搅拌摩擦焊制备铜铝合金双金属纳米复合材料

对纯铜与AA5754合金进行对接搅拌摩擦焊接。为了降低金属间化合物的有害影响,在搅拌摩擦焊(FSW)接头中添加纳米SiC强化颗粒。采用拉伸试验、显微硬度试验、扫描电镜和X射线衍射分析方法研究焊接接头的性能。结果显示,当焊接速度为50 mm/min、转速为1000 r/min时接头的性能最好。纳米SiC颗粒的存在使搅拌区(SZ)铝和铜的晶粒尺寸分别从38.3和12.4μm减小到12.9和5.1μm。含SiC纳米增强颗粒的接头其抗拉强度约为240 MPa,是铝基体的~90%。且添加SiC纳米颗粒使接头焊缝区的最高显微硬度从HV 160显著增加到HV 320。结果还表明,FSW接头中生成热的升高使Al_(4)Cu_(9)和Al_(2)Cu金属间化合物的数量增加。

采用Ag-Cu-Zn+Ni/Mn合金钎料的碳化钨钎焊接头的界面结构和力学性能（英文）

使用管式炉在高纯氩气中730℃下,以Ag-Cu-Zn+Ni/Mn合金为钎料焊接WC-Co硬质合金。研究钎焊时间和间隙尺寸对接头的影响。结果表明,焊接15 min,间隙尺寸为150μm的样品的最大剪切强度为(156±7)MPa。采用SEM,EDS和XRD手段表征钎焊接头的的特性和结构。焊接时间从5 min延长到15 min,为液体中间层流向基材提供了较好的机会。然而,当焊接时间超过15 min时,金属相如Mn_3W_3C的形成导致了接头的剪切强度降低。

Improvement of microstructure and corrosion properties of friction stir welded AA5754 by adding Zn interlayer

This study investigated the effect of Zn foil layers on the microstructure and corrosion characteristics of friction stir welded aluminum alloy 5754.Samples of various joints were prepared by applying different rotational and welding speeds,and their microstructures were evaluated via a metallographic technique and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy elemental analysis.The anticorrosion behavior of joints in the absence and presence of a Zn interlayer was studied by cyclic potentiodynamic polarization test in 3.5 wt% Na Cl aqueous solution,and sound welds were obtained in the presence of the Zn interlayer foil.The results revealed that the joint made at a rotational speed of 800 r/min and traveling speed of 15 mm/min achieved a chemical composition identical to that of aluminum alloy 7 xxx series,and as such,it showed the best resistance to corrosion.

Reduced graphene oxide (RGO) reinforced Mg biocomposites for use as orthopedic applications: Mechanical properties, cytocompatibility and antibacterial activity

Magnesium(Mg) has attracted wide interest in orthopedic applications as they exhibit great biodegradability and strong biocompatibility,while corrosion is the main concern for Mg that should be addressed prior to biomedical applications. In this work, ZM31(Mg-3Zn-1Mn)/x RGO(x = 0, 0.5, 1 and 1.5 wt%) biocomposites were synthesized by semi-powder metallurgy method. The results showed that the RGO acting as an effective reinforcing filler to prevent deformation and showed better compressive strength(282.3 ± 9 MPa) and revealed enhancement in failure Strain(7.8 ± 2.1%) at 1 wt% RGO concentration compared to Mg alloy(244.5 ± 9 MPa and 7.1 ± 1.5%respectively). Moreover, fracture analysis indicated a more ductile fracture of the nanocomposites after the incorporation of RGO. Crack bridging, crack deflection and crack branching are dominant mechanisms for reinforcement of Mg-based containing RGO. Mg composites containing 0.5 wt% RGO showed a low corrosion rate(2.75 mm/year), while more incorporation of RGO resulted in an increased corrosion rate(4.38 mm/year). In addition, the degradation rate of ZM31 alloy(2.57 mg·cm-2·d-1) obviously decreased with the addition of 0.5 wt%RGO(1.84 mg·cm-2·d-1) in the SBF. Besides, continuous apatite layers were created on the composites in the SBF solution. Also, the cell culture examinations showed good cell viability and adhesion on composites with 0.5 and 1 wt% RGO, which was demonstrated by the SEM and MTT assay The alkaline phosphatase(ALP) activity of the ZM3–0.5RGO composite was considerably higher than that of ZM31matrix alloy in 24 h and 48 h, implying higher osteoblastic differentiation. The antibacterial behavior toward both bacteria(E. coli and S.aureus) exhibited that escalating RGO concentration in Mg-matrix composites leads to further inhibition of bacteria growth. These findings suggested that ZM31–0.5RGO biocomposite could be a more promising candidate for orthopedic implants.

Dissimilar Joining of Pure Copper to Aluminum Alloy via Friction Stir Welding

In this study, the dissimilar friction stir welding （FSW） butt joints between aluminum alloy 5754-H114 and commerciallypure copper were investigated. The thickness of welded plates was 4 mm and the aluminum plate was placed on theadvancing side. In order to obtain a suitable flow and a better material mixing, a 1-mm offset was considered for thealuminum plate, toward the butt centerline. For investigating the microstructure and mechanical properties of FSWedjoints, optical microscopy and mechanical tests （i.e., uniaxial tensile test and microhardness） were used, respectively.Furthermore, the analysis of intermetallic compounds and fracture surface was examined by scanning electron microscopyand X-ray diffraction. The effect of heat generation on the mechanical properties and microstructure of the FSWed jointswas investigated. The results showed that there is an optimum amount of heat input. The intermetallic compounds formedin FSWed joints were A14Cu9 and AI2Cu. The best results were found in joints with 1000 rpm rotational speed and100 mm/min travel speed. The tensile strength was found as 219 MPa, which reached 84% of the aluminum base strength.Moreover, maximum value of the microhardness of the stir zone （SZ） was attained as about 120 HV, which was greatlydepended on the grain size, intermetallic compounds and copper pieces in SZ.

Surface Modification of Titanium by Producing Ti/TiN Surface Composite Layers via FSP

In this paper, we report the use of blowing nitrogen gas for the successful fabrication of a composite layer composed of Ti/TiN on a substrate of commercially pure titanium （cp-2） using the friction stir processing technique. The prepared composite layer was characterized by X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectrometry. The maximum microhardness of the Ti/TiN composite reached 1024 HV, which is 6.4 times higher than that of the titanium substrate. The results of wear test indicated that the Ti/TiN composite layer possesses excellent abrasive and adhesive wear resistance because of the formation of the TiN and its high hardness.