Amorphization of Co-base alloy by mechanical alloying

Structural transformations and the amorphization of cobalt base alloy particles are possible when a powder mixture of Co and Cr–Mo is subjected to the mechanical alloying (MA) process. Elemental powders mixed in adequate weight ratios were used as precursors. The process was carried out at room temperature in a shaker mixer mill using vials and balls of hardened steel as milling media, with a ball:powder weight ratio of 8:1. The characterization of the crystalline structure of milled powders was carried out by means of X-ray diffraction to analyze the phase transformations as a function of milling time. The aim of this work was to demonstrate that MA can induce the amorphization of Co–Cr–Mo alloy. The evolution of the phase transformation during milling time is reported. The results showed that it is possible to produce a partial solid solution at room temperature of elemental metallic powders Co70Cr30 and Co90Mo10 by mechanical alloying. Using specific experimental conditions, it is also possible to obtain an amorphous phase in a composition Co60Cr30Mo10; first, Cr and Mo were mechanically prealloyed for 9 h to obtain a Cr80Mo20 solid solution, and Co was then added and milled in over 14 h.

Research highlights
► High energy mechanical alloying can induce the amorphization of Co–Cr–Mo alloy.