Effect of mechanical processing on the stability of metastable icosahedral quasicrystalline nanoparticles in zirconium and hafnium based metallic glasses

• Metallic glasses were broken to small pieces by mechanical approaches.
• Unexpected phase transformations were observed.
• Approaches to avoid this negative effect were suggested.

Metastable icosahedral quasicrystalline nanoparticles precipitate in the initial crystallization processes of some selected zirconium and hafnium based metallic glasses. All such particles reported so far are embedded in residual glassy matrix. It is predicted that, if these are separated as free standing particles, they can be applied in a variety of fields. Breaking the suitably annealed metallic glasses to small pieces by mechanical approaches is considered to be the first step toward this goal. The result of such an attempt is reported here. Several previously reported metallic glasses such as Zr70Cu27.5Rh2.5 and Hf69.5Al7.5Ni11Cu12 have been abraded by using regular sandpapers and diamond papers, scraped with diamond scratchers, and sliced by using microtome. Thus obtained small pieces have been examined by Scanning Electron Microscope, Transmission Electron Microscope, and Energy Dispersive X-ray Spectroscopy. It has been revealed that the mechanical breaking processes cause an undesired phase transformation of the quasicrystalline nanoparticles to the crystalline phases. The reason for this undesired phase transformation was analyzed and the appropriate procedures to avoid this negative effect for future work were suggested.