Metallic amorphous nanocrystalline composites

Jan Dutkiewicz, Wojciech Maziarz, Lidia Lityńska-Dobrzyńska, Łukasz Rogal Adam Kanciruk, Andrea Kovačova 1-4 Instytut Metalurgii i Inżynierii Materiałowej PAN, ul. Reymonta 25, 30-059 Kraków, Poland 5 Instytut Mechaniki Górotworu PAN, ul. Reymonta 27, 30-059 Kraków, Poland 6 Department of Metal Forming, Technical University, Faculty of Metallurgy, Vysokoškolská 4, 042-00 Košice, Slovakia

Quarterly No. 3, 2008 pages 220-224

DOI:

keywords: ball milling, vacuum hot pressing, metallic amorphous nanocrystalline composites, TEM

article version pdf (1.39MB)

abstract Amorphous powder of composition corresponding to Ni60Ti20Zr20 (in at. %) was obtained by ball milling in a high energy mills starting from pure elements. Formation of the amorphous structure was observed already after 10 hours of milling, while complete amorphisation occured after 40 hours. Transmission electron microscopy allowed to identify nanocrystalline inclusions of intermetallic phases of size 25 nm. Uniaxial hot pressing at temperature below the crystallization Tx it is 530C and pressure of 600 MPa, of amorphous powders and nanocrystalline silver powders allowed to obtain composite, where amorphous phase microhardness is above 1000 HV and that of nanocrystalline silver 50% smaller. The nanocrystalline silver powder was prepared also by ball milling and the resulting grain size was measured using TEM at 2050 nm. Compression strength of the composite measure using testing Instron machine of a high stiffness is equal only to 500 MPa (it is much lower than for bulk amorphous) but at 3% of plastic strain, it is much better plasticity than for bulk amorphous materials. Both phases have similar values of Young’s modulus, however compression tests of composites gave much smaller values. Microstructure studies show low porosity of composites, less than 1%, uniform distribution of the silver phase and a small diffusion of nickel, titanium and zirconium toward silver, while the opposite diffusion toward the amorphous phase was insignificant. Future investigations will be directed toward lower porosity in order to improve strength and preserving good plasticity.