Phase transformations, thermal stability and forming studies of the ball-milled Cr70Co30 powders

Nanometric Cr ₇₀ Co ₃₀ powders mixture was obtained by ball milling from highly purified Cr and Co powders using a planetary ball mill under an argon atmosphere. Microstructural and structural parameters were deduced from Rietveld refinement of the XRD patterns. Thermal stability and forming of nanostructured Cr ₇₀ Co ₃₀ powders were studied by differential scanning calorimetry and sintering in solid phase at a heating temperature of 950 °C. The X-ray diffraction pattern reveals after 5 h of milling, the Co allotropic transformation from hcp structure to fcc structure. The formation of bcc-Cr(Co) solid solution was observed after 30 h. The DSC thermograms of the milled Cr ₇₀ Co ₃₀ powder exhibits an exothermic and endothermic peaks, which extend over the temperature range (100-1200) °C reflecting the structural relaxation, phase transformations, grain growth and magnetic transitions. The mechanical quantities such as H/E and H ³ /E ² are of about 9 and 152 GPa, respectively, after 30 h of milling.