Spark plasma sintering of Fe–Si–B–Cu–Nb / Finemet based alloys

The influence of mechanical alloying (MA) and spark plasma sintering (SPS) processing parameters on the microstructure, magnetic and mechanical properties of Finemet (Fe_73.5Cu₁Nb₃Si_13.5B₉) type alloys was investigated. Finemet alloy powder was obtained via mechanical alloying of elemental powders for 30 h, 60 h, 90 h, and 120 h with ball to powder ratio (BPR) of 10:1 and 15:1. The milled powders were consolidated using the SPS process. The XRD patterns confirm the presence of the α-Fe₃Si phase in all Finemet alloys, also broadening of the (110) peak of α-Fe₃Si was observed with increasing milling time. The microhardness of Finemet alloys increases with increase in milling time primarily due to a decrease in grain size. All samples show good saturation magnetization (M_s), 120h sample exhibiting the highest M_s of 166 emu/g, however coercivity increases with increasing milling time. Additionally, α-Fe₃Si crystal size decreases with increasing the BPR primarily due to higher impact energy.