Effect of Ni and Zr on the microstructural evolution of Ti-based alloys during ball-milling

In this paper, the effect of ball milling on Ti-based amorphous powders with nominal compositions of Ti48Cu39.5Ni10Co2.5 and Ti48Cu39.5Zr10Co2.5 (at.%) was studied. For this purpose, Ni and Zr containing crystalline master alloys were ball-milled for 20 h in total. According to XRD analysis, the maximal amorphous fraction has been achieved in the case of Ni containing powder after 5 h of milling. The nanocrystalline phase of CuTi3(Ni) having a grain size of 0.17-0.29 nm formed in the early stages of the milling process and remained stable until the end of milling. The amorphous-nanocrystalline transition of this phase is a reversible process. The amorphization process of Ti48Cu39.5Zr10Co2.5 is not so rapid than that in the Ni containing alloy system. This confirms that kinetic energy of the milling process is insufficient for destabilization of the Cu2ZrTi2 nanocrystalline (0.15-0.26 nm) phase. The microhardness of Ti48Cu39.5Ni10Co2.5 and Ti48Cu39.5Zr10Co2.5 particles was found to be HV0.01 519 ± 40 and 630 ± 55, respectively. For both compositions amorphous-nanocrystalline composites have been successfully obtained.