科研之友
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摘要
Powders of Al-50 wt-%Ni and Al-36 wt-%Ni were produced using the impulse atomisation technique, a rapid solidification technique. The molten droplets were cooled in flight by the stagnant helium or nitrogen in the atomising chamber. The resulting powders were sieved into different size ranges. X-ray diffraction and neutron diffraction were used in order to quantify the phase fractions in the samples. Profile refinement, using the computer software GSAS, was used to calculate the weight fraction of the existing phases, namely Al3Ni2, Al3Ni and Al, as a result of different processing parameters. The Scheil-Gulliver model was applied to investigate the extent to which it can predict phase fractions in the Al-Ni system. In Al-50 wt-%Ni, by increasing cooling rate, the ratio of Al3Ni to Al3Ni2 approaches that of Scheil-Gulliver's prediction. Opposite behaviour was observed in Al-36 wt-%Ni. In addition, from the profile refinement, the effect of composition and cooling rate on the lattice parameter of Al3Ni2 was investigated. In Al-36 wt-%Ni, the c/a ratio is significantly smaller than the stoichiometric c/a ratio of Al3Ni2, and it decreases with increasing cooling rate. On the other hand, for Al-50 wt-%Ni, the c/a ratio is much closer to the stoichiometric value and it increases with increasing cooling rate.
- 出版日期2011-7
