ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The crystallization of Ni60Nb40 metallic glass during continuous heating and isothermal annealing at temperatures from 845 to 904 K, was studied by differential scanning calorimetry (DSC), electrical resistance measurements, X-ray diffraction and transmission electron microscopy. Crystallization occurred in four clearly defined stages. In the initial stage a metastable phase, with structure similar to the M-phase in the Ni-Nb-Al ternary system, forms in the amorphous matrix. In the two subsequent stages the remaining glass crystallizes to the Ni3Nb- andΜ-phases found in the equilibrium Ni-Nb phase diagram. The M-phase transforms into the equilibrium Ni3Nb- andΜ-phases only at high temperature. The crystallization of the M-phase could be described by Johnson-Mehl-Avrami kinetics with the time exponentn=1.3 and activation energyE 1=628 kJ mol−1. M-phase crystal growth was apparently diffusion controlled and the diffusion coefficient was estimated to be 4.2×10−20 m2 sec−1. Activation energies for the second and third stages of crystallization were found to beE 2=446 kJ mol−1 andE 3 = 430 kJ mol−1.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00745579
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