Structure of the Ni-Co-Mn-In alloy obtained by mechanical alloying and sintering

A polycrystalline Ni45.5Co4.5Mn36.6In13.4 alloy was obtained by mechanical alloying during high energy ball milling. As-milled powders after 2.5 h, 5 h, 10 h, 15 h, 20 h, 30 h, 40 h, 50 h, 60 h and 70 of milling were studied in terms of structure, particle size and morphology, martensitic transformation. Selected powders were cold pressed and two-step sintered at 1253 K for 0.5 h and then at 1173 K for 24 h, followed by quenching into the ice-water mixture. The structure was examined by X-ray diffraction and electron microscopy. After 30 h of milling, solid-solution of nanocrystalline NiCoMnIn alloy with disordered body-centered cubic structure was observed. The microstructure of sintered samples revealed precipitates of γ particles inside of the matrix B2 grains, creating ‘subgrains’ of the matrix. The estimated average size of subgrains was around 60-70 μm.