Unusual strength-ductility synergy in immiscible W-Cu composites evoked by tailored hetero-zone boundary affected region

W-Cu composites are promising for diverse applications, yet their performance is limited by the fragile heterogeneous interface (HB) arising from the immiscibility of W/Cu. The heterogeneous boundary affected region (HBAR) plays a critical role in governing the cooperative mechanical response. Here, a multiscale heterogeneous structure was engineered within Cu phase, while abundant substructures were introduced into W phase by thermomechanical processing, forming HBARs characterized by pronounced strain gradients, effectively mediating deformation incompatibility between W/Cu. As a result, the designed W-30(Cu-5Al) (wt.%, WCA) composite achieved an ultrahigh strength-ductility synergy, providing a promising pathway for the structural applications of functional biphasic composites.