Cold pressing (CP) of the amorphous-like Co powder suppressed most of the XRD peaks, in particular the peak along (100) plane. The DSC curve of unmilled CP Co powder has shown a distinct sharp exothermic peak at 615◦C. Upon annealing at 700◦C, only the FCC phase with lattice parameter of 3.51 °A was detected by XRD. Our results implied that the exotherm at 615◦C corresponds to compaction-pressure-assisted HCP to FCC first-order phase transition. The XRD analysis of 30 h milled powder revealed for the first time the FCC phase with a = 3.80 A°. However, due to presence of (100) and (210) peaks, this phase is thought to be FCT with lattice parameters a = b = 3.80 and c = 3.07 A°. Consequently, the high-energy milling carried out in the current work induced for the first time HCP to FCT transition in Co. Upon CP of milled powder, the lattice parameter a shrunk from 3.80 to 3.75 A°. However, during annealing of the CP milled Co powder at 750◦C, the FCT to FCC transition occurred, yielding the FCC phase with a = 3.51 A°.
Reference:
Bolokang, AS, Phasha, MJ, Motaung, DE and Bhero, S. 2012. Effect of mechanical milling and cold pressing on co power. Journal of Metallurgy, pp 1-7
Bolokang, A., Phasha, M., Motaung, D., & Bhero, S. (2012). Effect of mechanical milling and cold pressing on co power. http://hdl.handle.net/10204/6614
Bolokang, AS, MJ Phasha, DE Motaung, and S Bhero "Effect of mechanical milling and cold pressing on co power." (2012) http://hdl.handle.net/10204/6614
Bolokang A, Phasha M, Motaung D, Bhero S. Effect of mechanical milling and cold pressing on co power. 2012; http://hdl.handle.net/10204/6614.
