Uncover the mystery of interfacial interactions in immiscible composites by spectroscopic microscopy: A case study with W-Cu

Characterizing immiscible metallic composites with electron microscopy and X-ray spectroscopy is the classic way of obtaining their structural and physical details. Nevertheless, such a combination lacks ability to tell the interfacial interactions at grain boundaries. Here we demonstrate a novel strategy to uncover the mystery of interfacial interactions in such systems by spectroscopic microscopy. The morphological and spectral data of samples were simultaneously recorded and analyzed, which reveals critical information regarding interfacial electronic modes. Taking W-Cu as a model, we experimentally quantified its connectivity and unambiguously identified conditional bonding between W and Cu. Further, we chemically reconstructed the specific W-Cu boundary that possessed the strongest interactions and investigated its atomic structure. The mechanism of W-Cu bonding was proposed and verified by first-principle calculations. The above methodology holds great promise to serve as a universal approach in achieving in-depth understanding of immiscible composites.