Nanocrystallization and mechanical properties of the amorphous Ni-Zr-Ti -Al-Cu -Si ribbons.
|Tomasz Czeppe , E. Vasileva , Jan M. Dutkiewicz|
Polish Academy of Sciences, Institute of Metallurgy and Materials Sciences (IMIM PAN), Reymonta 25, Kraków 30-059, Poland
In the paper the results concerning ribbons produced by the melt spinning on the rotating disc from the Ni56Zr18Ti16Al3Cu2Si5 alloy are presented. The ribbons were obtained at two different circumferential velocities and both revealed amorphous structure, what was confirmed by X-ray and the transmission electron microscopy (TEM) analysis. Differential scanning calorimetry (DSC) and differential thermal analysis (DTA) were used to determine basic parameters like glass transition temperature Tg, the onset of the primary crystallization Tx1 and liquidus temperature Tlq. The range of the supercooled liquid ΔTx=Tx1-Tg was determined as well as the reduced glass transition temperature Tg/Tlq=0.638, related to the GFA. The DSC was also used to determine the different stages of the isothermal crystallization of the ribbons and the activation energy for the crystallisation. The microstructure after nanocrystallization was observed using TEM and X-ray diffraction. The structure of ribbons was amorphous below Tg temperature. It was investigated after isothermal crystallization at temperatures: 560, 570, 580, 590 and 600oC. It was concluded that in agreement with works on NiTiZrSi alloys, the first crystallizing phase is the B2 NiTi(Zr). The average size of crystallites was 15 nm in diameter after isothermal crystallization during 20 min at 600oC. It was observed that even small particles of this phase might transform to martensite. The microhardness of the ribbons was measured at room temperature after different stages of the isothermal crystallization. It was found that the room temperature microhardness essentially increases during nanocrystallisation. The increase of the grains from nano- to the microcrystalline size has decreased microhardness down to about 1100 μHV.
Presentation: oral at E-MRS Fall Meeting 2003, Symposium G, by Tomasz Czeppe
See On-line Journal of E-MRS Fall Meeting 2003
Submitted: 2003-05-23 16:30 Revised: 2009-06-08 12:55