Effect of Mechanical Milling and Cold Pressing on Co Powder

Absract: Cobalt (Co) is a transition metal used in electronics, magnetic recording [1], and hard materials [2–4]. Through thermal [5] and mechanical treatment [6–9], Co metal undergoes the allotropic HCP to FCC phase transformation. The current literature shows that metastable FCC phase is induced by ball milling (BM) [6], cold pressing [10], and thermal treatments [11]. It has been shown in the previous investigations that Co milled with W, V, and C powders forms the complex FCC Co-rich carbide with large lattice parameters [12]. Apart from the FCC phase, Co-based alloys undergo amorphization via electrodeposition [13, 14] and mechanical alloying (MA) [15–17] and during irradiation processes [18, 19]. It is worth noting that in the case of milling, the XRD peaks of nonmetallic elements such as Si in a mixture with Co vanish rapidly when subjected to BM and ultimately lead to amorphization [17]. Similar behaviour occurs when a mixture of Co and metallic elements is subjected to milling [15, 16, 20]..