Experimental investigation of the Cu-Si phase diagram at x(Cu)>0.72

► Cu-Si phase diagram has been determined at x(Cu) > 0.72 by XRD, LOM, SEM, EPMA and DTA. ► ɛ-(Cu15Si4) phase is thermodynamically stable but kinetically inhibited by nucleation difficulties. ► Crystal structure and stability ranges of the high temperature β and δ phases have been especially investigated by XRD.