Anomalous Cu phase observed at HIP bonded Fe-Cu interface.

Hot isostatic pressing (HIP) processes are widely used for removing inner defects, densifying sintered components, consolidating particles and powders, and interfacial diffusion bonding. However, microscopic views of the phenomena have not been fully understood. X-ray absorption fine structure (XAFS) experiments were performed to study the interfacial region of the HIP bonded Fe-Cu sample. XAFS analyses clearly show that the bond distance around Cu is extraordinarily short compared with the bulk fcc Cu. The Cu species in the Fe-Cu HIP bonded sample takes a bcc structure even in the Cu-rich phase at room temperature. This anomalous bcc phase of Cu may derive from the HIP diffusion bonding process, which is performed below the melting points of both the elements. Cu atoms can diffuse into Fe with the bcc structure and settle in the bcc sites.