Recent work has shown that tungsten (W) and other refractory metals with body-centered cubic (bcc) structures exhibit certain novel behavior when their grain size, d, is refined into the ultrafine (UFG, 100 nm < d < 1000 nm) or nanocrystalline (NC, d < 100 nm) regime. For example, it has been shown that bcc refractory metals with such microstructures show decreased strain rate sensitivity besides their elevated strength and vanishing strain hardening response. Consequently, under both quasi-static and high-strain-rate loading, plastic instability in the form of shear banding becomes the dominant mode of plastic deformation. Such behavior is long sought-after in certain applications. However, due to the technology used to refine the grain size (primarily severe plastic deformation), the inability to scale the dimensions of the material may limit wider use and application of UFG/NC bcc refractory metals. In this work, the feasibility was demonstrated of production of large-scale W parts using a diffusion bonding method. The microstructure, preliminary mechanical properties, and issues and challenges associated with the fabrication procedures were examined and discussed. It is envisioned that diffusion bonding may serve as a promising technology for scaled-up fabrication of UFG bcc refractory metals for the targeted application.

最近的工作表明，当钨（W）和其他具有体心立方（bcc）结构的难熔金属的晶粒尺寸为d时，它们表现出某些新颖的行为。将其精制为超细（UFG，100 nm <d <1000 nm）或纳米晶体（NC，d <100 nm）方案。例如，已经表明具有这种微结构的密实cc耐火金属除了具有提高的强度和消失的应变硬化响应之外，还显示出降低的应变速率敏感性。因此，在准静态和高应变率载荷下，剪切带形式的塑性不稳定性成为塑性变形的主要方式。在某些应用中，长期以来一直追求这种行为。但是，由于用于细化晶粒尺寸的技术（主要是严重的塑性变形），无法缩放材料的尺寸可能会限制UFG / NC bcc难熔金属的广泛使用和应用。在这项工作中 证明了使用扩散结合法生产大规模W零件的可行性。研究和讨论了微观结构，初步的机械性能以及与制造程序相关的问题和挑战。可以预见，扩散结合可以用作有希望的技术，用于按目标应用规模生产UFG bcc难熔金属。