Abstract
Immiscible metallic composites are a class of promising materials with unique physical properties and excellent comprehensive mechanical properties. However, obtaining high-performance immiscible composites through solid-phase direct/indirect bonding processes has been a great challenge due to the difficulty of bonding and high melting-point difference in immiscible metal/alloy systems, especially immiscible W–Cu systems with the highest positive formation heat and high melting point variations. This work confirms that high-strength bonding between immiscible and highly melting-point-differentiated metals can be achieved under highly non-equilibrium transient liquid-phase direct bonding. Specifically, not only the construction of transient liquid-phase interfaces without interlayers between W and CuCrZr was realized under highly non-equilibrium conditions of melting/solidification and extremely high cooling rates brought about by the laser powder bed fusion additive manufacturing, but also the surface nanocrystallization was simultaneously obtained at the interface, forming the W/CuCrZr composite material with heterogeneous grain size structure. The W/CuCrZr composite materials possessed a gradient microstructure of micron-sized equiaxed tungsten grains, nano tungsten grains and columnar Cu grains in sequence as well as having excellent interfacial bonding strength and a high effective bonding area ratio. By combining experiments and molecular dynamics simulations, it was clarified that the introduction of crystal defects and the formation of tungsten nanograins promote the diffusion of immiscible W and Cu and achieve strong bonding. Our work provides a new strategy and in-depth view into the fabrication of excellent-performance composite materials between immiscible metals/alloys.
Published Version
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