基于添加铜过渡层的钛钢异种金属真空扩散焊研究

研究了添加铜箔过渡层进行扩散焊接的纯钛TA2和14MnMoVN钢焊接接头的组织和性能.采用OM、扫描电镜、能谱分析和X射线衍射分析对扩散焊接界面的微观组织、元素扩散和组织结构进行分析观察,通过拉伸试验对接头力学性能进行测试.结果表明:通过添加铜过渡层进行扩散焊接可以获得有效连接的钛/钢异种金属复合接头.结合良好的界面可以划分为接头元素扩散过渡区和铜钛结合区.其中钛向铜扩散,少量铁向铜扩散,这是三种元素的综合扩散过渡区.铜钛结合区是铜向钛扩散的区域,主要产生大量的铜钛金属间化合物.接头拉伸强度可以达到299 MPa,断裂位置位于铜钢结合区.

Enhancement of nucleation of diamond films deposited on copper substrate by nickel modification layer

A Ni layer with a thickness of about 100 nm was sputtered on Cu substrates,followed by an ultrasonic seeding with nanodiamond suspension.High-quality diamond film with its crystalline grains close to thermal equilibrium shape was deposited on Cu substrates by hot-filament chemical vapor deposition（HF-CVD）,and the sp2 carbon content was less than 5.56%.The nucleation and growth of diamond film were investigated by micro-Raman spectroscopy,scanning electron microscopy,and X-ray diffraction.The results show that the nucleation density of diamond on the Ni-modified Cu substrates is 10 times higher than that on blank Cu substrates.The enhancement mechanism of the nucleation kinetics by Ni modification layer results from two effects：namely,the nanometer rough Ni-modified surface shows an improved absorption of nanodiamond particles that act as starting points for the diamond nucleation during HF-CVD process;the strong catalytic effect of the Ni-modified surface causes the formation of graphite layer that acts as an intermediate to facilitate diamond nucleation quickly.

Solidification process and microstructure of transition layer of Cu-Al composite cast prepared by method of pouring molten aluminum

The Cu?Al composite casts were prepared by the method of pouring molten aluminum. The solidification process and themicrostructure of the transition layer were investigated during the recombination process of the liquid Al and the solid Cu. The results reveal that the microstructure of the transition layer in the Cu?Al composite cast consists of α(Al)+α(Al)?CuAl2 eutectic,α(Al)?CuAl2 eutectic, CuAl2+α(Al)?CuAl2 eutectic and Cu9Al4. Additionally, the pouring temperature, cooling mode of the Cu platesurface and start time of the forced cooling after pouring have no effect on the microstructure species. But the proportion of thevarious microstructures in the transition layer changes with the process parameters. The pure Al at the top of the transition layer startsto solidify first and then the α(Al) phase grows in a dendritic way, while the CuAl2 phase exhibits plane or cellular crystal growth from the two sides of the transition layer towards its interior. The stronger the cooling intensity of the Cu plate outer surface, the more developed the dendrite, and the easier it is for the CuAl2 phase to grow into a plane crystal.

Modifying element diffusion pathway by transition layer structure in high-entropy alloy particle reinforced Cu matrix composites

The Al0.3CoCrFeNi high-entropy alloy(HEA)particles reinforced Cu matrix composites(CMCs)were fabricated by mechanical alloying and sintering.Transition layer structure was obtained by multi-step ball milling to investigate the related influence on element diffusion behavior and wear properties of CMCs.The results indicate that a new Cu transition layer is generated,and the thickness is about 5μm.Cr element diffuses into the interface via the transition layer,which forms the complex oxide.Because of the structure of Cu transition layer,the diffusion rates of Ni,Co and Fe increase,especially the Ni element.The wear resistance of CMCs is improved by 30%,which is due to the improvement of interface bonding strength,compared with the CMCs without transition layer.This method is applicable to the development of advanced HEA reinforced metallic matrix composites.

Interfacial microstructure of Cu Cr/1Cr18Ni9Ti bi-metal materials and its effect on bonding strength

The Cu Cr/1Cr18Ni9 Ti bi-metal materials were prepared by the solid-liquid bonding method. The microstructures, mechanical properties and formation mechanism of the bonding interface were studied. The results show that there exists a serrated transition layer with a certain width at the interface of Cu Cr/1Cr18Ni9 Ti bi-metal materials, and the transition layer consists of Fe-based and Cu-based solid solutions. The elastic modulus and hardness reach the maximum values at the interface closing to the 1Cr18Ni9 Ti zone. The bonding temperature has a significant effect on the width and morphology of the transition layer. The interfacial bonding strength is at least 30% higher than that of the Cu Cr alloy, and the tensile fracture occurs at the side of the Cu Cr alloy rather than at the bonding interface.