Formation and growth mechanism of Cu-rich layer at aluminum/steel friction welding interface

Utilizing friction welding to achieve the high-quality bonding of 2219 aluminum (Al) alloy/304 stainless steel dissimilar materials has promising applications in aerospace and other industrial fields. The formation of the Cu-rich layer is a distinctive feature that distinguishes it from other series Al alloy/steel friction welding joints. Currently, a summary of the relevant literature reveals that there are three main possible formation mechanisms for the Cu-rich layer: diffusion mechanism, liquefaction mechanism and strengthening phase accumulation mechanism. In this paper, these three formation mechanisms are denied experimentally. Meanwhile, it is proposed that the formation and growth mechanism of the Cu-rich layer is strengthening phase precipitation-reaction-reprecipitation mechanism. The correctness of this theory has also been proved by experiments. The proposed model can facilitate the improvement of the friction welding process of dissimilar materials and provide a theoretical basis for the regulation of the metallurgical reaction of the friction welding joint

Microstructure evolution and tensile strength of Al/Cu inertia friction welded joint

To save production costs and reduce the weight of structures, it is one of the common ways to replace copper (Cu) with aluminum (Al) in some industries such as the refrigeration industry. The high-quality welding of Al to Cu determines the application of the Al/Cu hybrid structure. The inertia friction welding process was used to weld Al pipe to Cu pipe and the Taguchi experiment method was used to study the effects of inertia friction welding parameters on the mechanical properties of the welded joints, and the results show that the initial speed has the greatest influence on the tensile strength of welded joints. Meanwhile, the analyses of the microstructures of the joint show that Al–Cu IMCs formed at the friction interface to realize the metallurgical bonding of the welded joints. The formation sequence of Al–Cu IMCs in the friction welding process is Al2Cu, Al4Cu9, and AlCu. Whereas the type and thickness of IMCs are closely related to the tensile strength of the joints. When the welded joint forms Al2Cu and Al4Cu9, the interfacial misfit between the IMCs layer and base materials is minimized and the tensile strength of the joint is optimized

Multiple Synergistic Drilling Fluid System Application in Aihu Oilfield

The unstable layer of Aihu oilfield is characterized by strong hydration dispersion and weak expansion. The theory of multiple synergistic wall stabilization was applied to improve synergistic efficiency of the drilling fluid. The recipe of multiple synergistic drilling fluid is worked out. The multiple synergistic drilling fluid was evaluated by analysing the rheology, filtration, wall building, inhibition for the borehole & the weak layers. The inhibition and rheology of the tested drilling fluid system is as good as anti-temperature performance. The ternary-inhibitive drilling fluid system is superior to the binary-inhibitive drilling fluid system. The ternary-inhibitive contained in the multiple synergistic drilling fluid system enhances the ability of water dispersion inhibition. The application of Aihu oilfield shows that the multiple synergistic drilling fluid has satisfied the requirements of low filtration and slight wall expansion

Effect of thermo-mechanical distribution on the evolution of IMCs layer and mechanical properties of 2219 aluminum alloy/304 stainless steel joints by inertia friction welding

The hybrid structure of 2219 aluminum alloy (Al alloy) and 304 stainless steel is effectively joined by inertia friction welding. There are the Cu-rich layer and the Fe4Al13 layer in the friction interface. The Cu-rich layer is discontinuous and its thickness is not uneven. While the Fe–Al layer is continuous and its thickness is closely related to the thermo-mechanical distribution at the interface. The thickness of the Fe–Al IMCs layer in the 1/2 radius zone is 6 fold of that in the center, while the center zone has unbonding defects due to low temperature and poor plastic flow of Al alloy. However, after changing the shape of the Al alloy end face, especially for the tapering surface joint, the homogeneous layer of Fe–Al IMCs forms in the center and 1/2 radius zones, which makes the tensile strength of different zones of the joint more balanced and improves the integral tensile strength. Meanwhile, the evolution of the two IMCs layers was investigated. It is found that the Cu-rich layer is formed through the precipitation of Al2Cu in the Al alloy. While the Fe–Al layer is formed through atomic interdiffusion and its growth is influenced not only by the thermo-mechanical coupling but also the precipitation of the Al2Cu phase

Carbon Nanofibers Decorated by MoS2 Nanosheets with Tunable Quantity as Self-Supporting Anode for High-Performance Lithium Ion Batteries

Two-dimensional molybdenum disulfide (MoS2) is considered as a highly promising anode material for lithium-ion batteries (LIBs) due to its unique layer structure, large plane spacing, and high theoretical specific capacity; however, the overlap of MoS2 nanosheets and inherently low electrical conductivity lead to rapid capacity decay, resulting in poor cycling stability and low multiplicative performance. This severely limits its practical application in LIBs. To overcome the above problems, composite fibers with a core//sheath structure have been designed and fabricated. The sheath moiety of MoS2 nanosheets is uniformly anchored by the hydrothermal treatment of the axial of carbon nanofibers derived from an electrospinning method (CNFs//MoS2). The quantity of the MoS2 nanosheets on the CNFs substrates can be tuned by controlling the amount of utilized thiourea precursor. The influence of the MoS2 nanosheets on the electrochemical properties of the composite fibers has been investigated. The synergistic effect between MoS2 and carbon nanofibers can enhance their electrical conductivity and ionic reversibility as an anode for LIBs. The composite fibers deliver a high reversible capacity of 866.5 mA h g−1 after 200 cycles at a current density of 0.5 A g−1 and maintain a capacity of 703.3 mA h g−1 after a long cycle of 500 charge–discharge processes at 1 A g−1