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A technique for producing impact welds with small standoff gaps between dissimilar aluminum alloys, using the Vaporizing Foil Actuator Welding technique, is demonstrated here with the joining of aluminum 6061-T6 to aluminum 7075-T6. One-millimeter-thick AA6061-T6 flyers were welded to a 3-mm thick 7075-T6 target with a nominal standoff gap of just 0.3mm. This small standoff gap is an improvement compared to other impact welding work, allowing for less deformation in the flyer sheet. The welds exhibited remarkable consistency in their failure loads during tensile tests, with nugget pullout mode failure in all samples at failure loads similar to or exceeding those of a comparably sized rivet. Cyclic testing was not as repeatable as the static testing. While the method adopted here requires bare metal surfaces for welding, the process can make joints without damage to nearby coated surfaces. A geometric model is proposed to help explain how sufficient impact angles are generated over standoff distances of 0.3mm or less. The model agrees well with the morphology of the welded and unwelded areas produced in this work and may be useful for predicting impact angles as a function of the standoff distance and the shape of the foil actuator used to launch the flyer to high impact speeds. [ABSTRACT FROM AUTHOR]

Vaporizing foil actuator welding (VFAW) was used for joining 2024-T3 and 7075-T6 aluminum alloy sheets, and the resulting joint microstructure was analyzed. 2024/7075 aluminum alloy pairs with suitable processing parameters can be prepared by using VFAW. Dynamic preform addresses the poor formability problem of target material and advantage of VFAW on dissimilar materials in some conditions. But with standoff sheet inserting in the flyer and target, 2024/7075 welded pairs gets the better weld strength, compared with flyer preformed method. The microstructure of the circular weld area of the welded joint showed a wave interface, in which a thin melt layer formed at the center and edge parts. The crystal grains near the bonding interface were remarkably elongated and refined. Therefore, the joining of the 2024/7075 pairs was facilitated through plastic forming and melting. [ABSTRACT FROM AUTHOR]

Explosive welding involves processes like the detonation of explosive, impact of metal structures and strong fluid-structure interaction, while the whole process of explosive welding has not been well modeled before. In this paper, a novel smoothed particle hydrodynamics (SPH) model is developed to simulate explosive welding. In the SPH model, a kernel gradient correction algorithm is used to achieve better computational accuracy. A density adapting technique which can effectively treat large density ratio is also proposed. The developed SPH model is firstly validated by simulating a benchmark problem of one-dimensional TNT detonation and an impact welding problem. The SPH model is then successfully applied to simulate the whole process of explosive welding. It is demonstrated that the presented SPH method can capture typical physics in explosive welding including explosion wave, welding surface morphology, jet flow and acceleration of the flyer plate. The welding angle obtained from the SPH simulation agrees well with that from a kinematic analysis. [ABSTRACT FROM AUTHOR]

Microsample tensile testing was conducted to evaluate the quality of impact welds created by vaporizing foil actuator welding. Tensile test samples with a gauge length of 0.6 mm were electro-discharge machined out of welds created between 1-mm-thick aluminum alloy type 6061 (AA6061) sheets and 6-mm-thick copper (Cu110) plates. Aluminum sheets were used as flyers, while copper plates acted as targets. Flyer sheets in T6 as well as T4 temper conditions were utilized to create welds. Some of the welds made with T4 temper flyers were heat treated to a T6 temper. It was found that the welds made with T4 temper flyers were slightly stronger (max. of 270 MPa) than those produced with T6 temper flyers. Generally, failure propagated in a brittle manner across the weld interface; however, elemental mapping reveals material transfer on either member of the welded system. This work proves the feasibility to apply microsample tensile testing to assess impact welding, even when conducted with flyer sheets of 1 mm or less, and provides insight that is complementary to other test methods. [ABSTRACT FROM AUTHOR]