Pressureless liquid-phase sintering of copper with a mechanically milled Cu–Ag eutectic-composition premix

Pressureless liquid-phase sintering of Cu containing a mechanically milled 28Cu–72Ag (wt.%) premix was investigated to relate premix content and thermal history to densification, microstructure, hardness and electrical conductivity. Cu blends containing 0–40 wt.% premix were processed using five schedules that varied heating rate and holding time. Increasing premix content enhanced densification despite lowering green density. D120–Cu–40Et gave the largest mean relative density (∼93.4%), while H20–Cu–40Et reached ∼92.2% after 15 minutes at 800◦C. Longer high-temperature exposure refined pores and increasingly rounded Cu-rich regions at higher premix contents, whereas rapid heating retained finer, heterogeneous Ag-rich intergranular regions. X-ray diffraction and energy-dispersive spectroscopy identified mutually soluble Curich and Ag-rich face-centred-cubic phases without additional crystalline intermetallics. When combined hardness and conductivity are prioritised, with density and hold duration as trade-offs, H20–Cu–40Et is the single recommended tested condition: (67.9 ± 2.3) HV0.1 and (77.9 ± 2.0)% IACS. D120–Cu–40Et is the density benchmark, not a second overall optimum; the recommendation is based on observed means without significance testing.