Mechanical and magnetic properties of phase separated Cu50Fe50 (at%) alloys synthesized by mechanical alloying and spark plasma sintering

A bulk Cu 50 Fe 50 (at%) alloy was prepared by mechanical alloying (MA) of elemental Cu and Fe powders for 20 h, followed by the spark plasma sintering (SPS). All the powder and bulk samples were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanical and magnetic properties of the bulk samples were also evaluated. From 1 h to about 10 h of milling, the formation of nanocrystalline Cu-rich facecentered cubic solid solution (FCC gamma phase) and Fe-rich body -centered cubic solid solution (BCC alpha phase) was observed. Above 10 h of milling, the gamma and alpha phases merged to form a single-phase face -centered cubic (gamma S ) solid solution till 20 h. Subsequently, the 20 h MA powder was consolidated using spark plasma sintering (SPS) at three different temperatures: 519 degrees C (0.5 T m ), 677 degrees C(0.6 T m ), and 835 degrees C (0.7 T m ), where T m is the average melting point of the alloy (1310 degrees C). In all three samples, the metastable gamma S phase decomposed into the nanocrystalline Cu-rich gamma and Fe-rich alpha phases during SPS. Notably, the 0.7 T m sample exhibited a better balance between strength and ductility by demonstrating a compressive yield strength of 886 MPa and an ultimate compressive strength of 1166 MPa with a ductility of 15%. The high strength and ductility are attributed to a bimodal grain size distribution, i.e., a few microns thick and continuous Cu-rich gamma grain boundary phase and an intragranular nanocrystalline mixture of gamma and alpha phases. In addition to its excellent mechanical properties, the 0.7 T m sample displayed favorable soft ferromagnetic characteristics exhibiting a saturation magnetization (M s ) of 66 emu/g and a coercivity (H c ) of 16 Oe.