Mechanical Properties of Cu₇₀Fe₃₀ (at%) Bulk Metastable Alloys Prepared by Mechanical Alloying and Spark Plasma Sintering

The equilibrium‐insoluble Cu and Fe metals with a composition of Cu₇₀Fe₃₀ (at%) are mechanically milled for 20 h, resulting in a metastable single‐phase face‐centered cubic supersaturated solid solution (γ^S). The alloy powders are consolidated by spark plasma sintering (SPS) at 0.6T_m (622 °C) and 0.7T_m (772 °C), where T_m is the melting point of Cu₇₀Fe₃₀ (1219 °C). Scanning electron microscopy (SEM), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and electron backscatter (EBSD) analyses are performed on mechanically alloyed powders and SPS bulk samples. Compressive stress–strain and hardness tests are also conducted on the bulk SPS samples to evaluate the mechanical properties. The metallographic study reveals that the γ^S phase decomposes into Cu‐rich γ and Fe‐rich α phases after SPS. The 0.6T_m sample exhibits a continuous γ‐network phase surrounding an ultrafine γ + α mixture, causing brittle behavior due to crack propagation during compressive testing. In contrast, the 0.7T_m sample features a discontinuous γ‐network phase, enhancing ductility and resulting in a bimodal grain structure. This sample demonstrates superior mechanical properties, combining excellent strength (1056 MPa) and ductility (23%) due to the coexistence of coarser γ‐network grains (1–2 μm) and ultrafine γ + α grains (200–500 nm).