Interfacial microstructure and strength of brazed copper/porous copper foam towards the effect of porous copper foam pore density and brazing holding time

The porous copper foam was sandwiched between two coppers plate and then brazed using copper-tin (9.7 %)-nickel (5.7 %)-phosphorus (7 %) filler foil. Brazing process was conducted to joint copper/porous copper foam by evaluating the effect of porous copper foam pore densities [pore per inch (PPI)] and brazing holding times. The brazed joint interface of copper and porous copper foam was characterised using Field emission scanning electron microscopy and Energy-dispersive x-ray spectroscopy for the microstructure and elemental composition analysis, respectively. X-ray diffraction analysis was carried out on the shear fractured surfaces of brazed copper and porous copper foam for phase determination. The results exhibited distinct phases of copper (Cu), copper phosphide (Cu₃P), nickel phosphide (Ni₃P), and copper compound with tin (6 : 5) (Cu₆Sn₅). The filler layer was formed as an island-shaped that consists of copper phosphide and nickel phosphide. Prolong brazing holding time causes a thinner filler layer in brazing seam. While the non-uniform thickness of the filler layer was observed at different pore densities of porous copper foam. The shear strength of brazed copper/porous copper foam 15 PPI with a 10 min brazing holding time yield a maximum shear strength of 2.9 MPa.     

Brazing temperature-dependent interfacial reaction layer features between CBN and Cu-Sn-Ti active filler metal

CBN/Cu-Sn-Ti (CBN: cubic boron nitride) composites are prepared by active brazing sintering at 1123 K, 1173 K, 1223 K and 1273 K, respectively. The effects of brazing temperature on the wettability, interfacial characteristics, and elemental distribution variations are fully investigated. When the brazing temperature is below 1223 K, completely uncoated and/or partially coated CBN particles with sharp edges can still be observed, and the reaction layer, mainly composed of TiN and TiB2, appears to be thin and uneven. When the brazing temperature is 1223 K, all CBN particles are completely coated, suggesting that adequate wetting has taken place. Besides, as Ti diffuses thoroughly and enriches the interface, the reaction layer, filled primarily by TiN, TiB₂ and TiB, becomes thicker (about 1.30 μm), more uniform, stable and continuous. Further increasing the temperature to 1273 K is unnecessary or even harmful as the reaction layer thickness undergoes negligible change yet some tiny micro-cracks appear on the interface, which may likely deteriorate the grinding capability of the final brazing products.     

Effect of BAg1 Ni-Electroplating on microstructure and properties of WC-Co-brazed joints

Excellent strength, joining effectiveness and low cost of brazing make it one of the most favoured methods for hard metals attachments. In this study, WC-Co, as a hard metal, was furnace-brazed by BAg1 (Ag–Cu–Zn–Cd) filler alloy and Ni-electroplated BAg1, and the influence of Ni-electroplating in joint properties was thoroughly studied. The brazing process was carried out using a tube furnace, at 670°C/15?min. The characteristics and microstructure of joints were studied by scanning electron microscope, energy-dispersive spectrometer and XRD. It was revealed that Ni coating of BAg1 represents 20% increase in wettability and approximately 15% increase in shear strength (from 107.98 to 124.17?MPa) by the formation of soft and semi-active NiZn phase and by the substitution of some of brittle TiC phase with NiTi phase.     

梯度三明治银基钎料复合界面组织及生长动力学研究

针对梯度钎料轧制过程中易出现撕裂的问题,借助扫描电镜、EDS 能谱仪、万能力学试验机等手段研究气保护热压复合BAg40CuZnNi/CuMn2/BAg40CuZnNiMnCo梯度三明治复合钎料均匀化退火工艺对界面扩散组织和性能的影响规律,探明复合界面生长行为,为优化退火工艺提供技术参考。研究结果表明:热压复合界面扩散层主要为富铜相、富银相;随均匀化退火时间的延长,界面两侧元素不断发生互扩散,界面结合强度有所下降,当保温时间在5 ~18 h时强度稳定在180 MPa左右。继续延长时间,界面扩散层厚度超过20 μm,脆性的AgZn₃相尺寸不断粗化增大,强度由初始态的260 MPa下降到100 MPa左右,导致复合钎料在轧制过程中出现开裂。退火不同时间后,界面扩散层厚度逐渐增加,其趋势符合抛物线法则;当退火温度达823 K,保温18 h时,扩散层厚度由原来的12.5 μm增加到22.4 μm;运用Arrhenius方程计算得出界面扩散层生长激活能为20.810 8 kJ/mol,并获得其生长动力学模型,通过此模型可对扩散层厚度进行初步计算。     

Microstructure and XRD analysis of brazing joint for duplex stainless steel using a Ni–Si–B filler metal

Brazing of a nitrogen-containing duplex stainless steel was preformed using a nickel-based filler metal (Ni-4.5wt.%, Si-3.2wt.%, B). The microstructure of the brazed joint was investigated using scanning electron microscopy, energy dispersive spectrometry, electron probe microanalyzer, and layer-by-layer X-ray diffraction analysis. The results indicated that before completion of isothermal solidification, BN, Ni₃B and Ni₃Si precipitates formed at the interface, in the athermally solidified zone and isothermally solidified zone, respectively. After isothermal solidification, only γ-Ni phase appeared in the brazed interlayer. The appearance of hardness peak values in the athermally solidified zone and the interface most probably corresponded to the formation of Ni₃B and BN, respectively.     

Zr-Cu-Ni非晶钎料真空钎焊TiAl合金/316L不锈钢接头的界面组织与剪切性能

采用自主设计制备的Zr-42.9Cu-21.4Ni非晶钎料对TiAl合金和316L不锈钢进行真空钎焊,研究钎焊温度和钎焊时间对TiAl合金/316L不锈钢异种金属接头微观组织和剪切性能的影响。结果表明：钎缝界面可以划分为6个不同的反应层。1040 ℃/10 min下制备的钎焊接头从TiAl合金到316L不锈钢侧界面组织依次为γ(TiAl)+AlCuTi/α₂(Ti₃Al)+AlCuTi/AlCu+ZrCuNi+FeZr/Cu₈Zr₃+ZrCuNi+TiFe+Fe₂Zr/FeZr+Fe₂Zr+TiFe₂+ZrCu/α-(Fe, Cr)。随着钎焊温度的升高,接头的抗剪强度先升高后降低。当钎焊温度为1040 ℃和钎焊时间25 min时,接头抗剪强度达到最大值162 MPa。断口分析表明,接头在FeZr+Fe₂Zr+TiFe₂+ZrCu界面处萌生,沿着Cu₈Zr₃+ZrCuNi+TiFe+Fe₂Zr和α-(Fe, Cr)扩展,呈解理断裂。     

电场对异种金属摩擦焊接头组织与性能的影响

研究了外加电场对T2紫铜和1Cr18Ni9Ti不锈钢摩擦焊接头焊合区的显微组织、主要合金元素的扩散区宽度以及接头力学性能的影响．结果表明，外加电场加快了焊合区金属的动态再结品进程，不同形式的电场对焊合区铜侧的组织形态与分布有不同的影响．在负电场(试件接电源负极)作用下，焊合区金厦发生的动态再结晶程度最大，品粒尺寸较大且分布均匀；交流电场使品粒尺寸略有减小．交流电场和负电场通过对金厦内部电子密度的影响，促进了焊接过程中焊缝区Cu、Pe和Cr的扩散，并提高了焊接接头扭转强度。     

Experimental investigation of local tensile and fracture resistance behaviour of dissimilar metal weld joint: SA508 Gr.3 Cl.1 and SA312 Type 304LN

The aim of the paper is to evaluate the local tensile and fracture toughness properties of the dissimilar metal weld joints between SA508Gr.3 Cl.1 and SA312 Type 304LN pipe. Weld joints have been prepared by manual gas tungsten arc welding (GTAW) process with conventional V‐groove and automatic hot wire gas tungsten arc welding with narrow gap using different filler wires/electrode such as Inconel 82/Inconel 182 and ER309L/ER308L. The tensile and fracture toughness test specimens have been machined from different regions of dissimilar metal weld such as heat affected zones, fusion lines, buttering layer, weld metal and both base metals. Tensile and fracture toughness tests have been carried out as per the ASTM standard E8 and E1820 respectively. Tensile and fracture toughness results of all the regions of dissimilar metal weld joints have been discussed in this paper. Metallurgical and fracture surface examinations have also been reported to substantiate the tensile and fracture toughness results. Need for the local properties for integrity assessment of the dissimilar metal weld joints has also been brought out.