Cluster‐Driven Strengthening and Oxide Stripes‐Induced Embrittlement in Internally Oxidized AgMg Alloys

ABSTRACT Internal oxidation has been identified as an effective method for enhancing the strength of AgMg alloys. However, the concurrent occurrence of embrittlement remains inadequately understood, thus limiting their broader application. This study investigates the oxidation behavior of AgMg alloys with Mg concentrations ranging from 1 at% to 7 at% at 800°C, revealing a composition‐dependent evolution of microstructure and mechanical properties. The oxidation process results in the formation of two distinct zones: a Mg/O solid solution zone (Mg/O SSZ), characterized by ∼3 nm Mg/O clusters, and an internal oxide band zone (IOBZ), where nanocrystalline MgO stripes emerge at Mg concentrations of 2 at% or higher. The Mg/O SSZ is responsible for substantial strengthening, with surface hardness increasing from 74 HV (as‐cast) to 224 HV at 7 at% Mg, and tensile strength rising from less than 50 MPa (pure Ag) to 269 MPa at 1 at% Mg. In contrast, the development of MgO stripes within the IOBZ induces localized stress concentrations at incoherent MgO/Ag interfaces, resulting in embrittlement and a reduction in mechanical performance at higher Mg contents. The oxidation kinetics deviate progressively from Wagner's theory with increasing Mg concentration, as the formation of MgO stripes impedes oxygen transport, decreasing the oxidation rate from 7.83 μm s −1/2 at 1 at% Mg to 0.69 μm s −1/2 at 7 at% Mg. These results elucidate a compositionally tunable balance between nanoscale cluster‐driven strengthening and oxide stripe‐induced embrittlement, providing a mechanistic framework for the design of high‐performance AgMg alloys for structural and electronic applications.