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Magnetic pulse welding is a solid state impact welding process, similar to explosive welding, which produces metallurgical bond by oblique high-speed impact between two metal bodies. This violent impact removes the metal surface oxide layers and then joins the two atomic level clean metal surfaces together by the incidental compression pressure. The impact velocity is at 200–400 m/s and the being welded metal surface undergoes severe plastic deformation with strain rate in the order of 106–107 s−1. The ultrafine-grained structure was observed on the welded interface. This article studied two types of similar material lap joint interfaces and the base metals were aluminum alloy 6061 and copper alloy 110. Nano-indentation testing shows that the welded interfaces have significantly greater hardness than the base metals. The interface microstructure was studied by optical microscopy, electron backscatter diffraction microscopy, and transmission electron microscopy. The welded aluminum alloy 6061 interface exhibits extremely fine grains and an extremely high dislocation density. The impact welded copper alloy 110 interface presents nano-scale lamellar band structure and deformation twins. The interface hardness increasing was attributed to this impact-induced microstructural refinement. [ABSTRACT FROM AUTHOR]

Ultrasonic additive manufacturing (UAM) is a solid-state process, which uses ultrasonic vibrations at 20 kHz along with mechanized tape layering and intermittent milling operation, to build fully functional three-dimensional parts. In the literature, UAM builds made with low power (1.5 kW) exhibited poor tensile properties when loaded along the Z-direction, i.e., normal to the interfaces. This reduction in properties is often attributed to the lack of bonding at the interfaces. The generality of this conclusion is evaluated further in 6061 aluminum alloy builds made with very high power UAM (9 kW). Tensile deformation behavior along X and Z directions were evaluated with small-scale in-situ mechanical testing equipped with high-resolution digital image correlation, as well as, multi-scale characterization of builds. Interestingly, even with complete metallurgical bonding across the interfaces without any discernable voids, poor Z-direction properties were observed. This reduction is correlated to coalescence of pre-existing shear bands at interfaces into micro voids, leading to strain localization and spontaneous failure on tensile loading. [ABSTRACT FROM AUTHOR]