Abstract: The pursuit of Ag-based alloys with both high strength and toughness has posed a longstanding challenge. In this study, we investigated the cluster strengthening and grain refinement toughening mechanisms in fully oxidized AgMgNi alloys, which were internally oxidized at 800 °C for 8 h under an oxygen atmosphere. We found that Mg-O clusters contributed to the hardening (138 HV) and strengthening (376.9 MPa) of the AgMg alloy through solid solution strengthening effects, albeit at the expense of ductility. To address this limitation, we introduced Ni nanoparticles into the AgMg alloy, resulting in significant grain refinement within its microstructure. Specifically, the grain size decreased from 67.2 μm in the oxidized AgMg alloy to below 6.0 μm in the oxidized AgMgNi alloy containing 0.3 wt% Ni. Consequently, the toughness increased significantly, rising from toughness value of 2177.9 MJ m^-³ in the oxidized AgMg alloy to 6186.1 MJ m^-³ in the oxidized AgMgNi alloy, representing a remarkable 2.8-fold enhancement. Furthermore, the internally oxidized AgMgNi alloy attained a strength of up to 387.6 MPa, comparable to that of the internally oxidized AgMg alloy, thereby demonstrating the successful realization of concurrent strengthening and toughening. These results collectively offer a novel approach for the design of high-performance alloys through the synergistic combination of cluster strengthening and grain refinement toughening.

Key words: Ag-based alloys, Mg-O cluster, Grain refining, Internal oxidation, Hardening