Influence of chemical composition and alloying
elements on microdefects and electron density
in Ni-Al alloys
elements on microdefects and electron density
in Ni-Al alloys
(1. Physics Department, Guangxi University,
Nanning 530004, China;
2. Institute of Metal Research, The Chinese Academy of Sciences,
Shenyang 110016, China；
3. International Centre for Materials Physics,
The Chinese Academy of Sciences, Shenyang 110016, China)
Nanning 530004, China;
2. Institute of Metal Research, The Chinese Academy of Sciences,
Shenyang 110016, China；
3. International Centre for Materials Physics,
The Chinese Academy of Sciences, Shenyang 110016, China)
Abstract: Positron lifetime spectra have been measured in binary Ni-Al alloys with different chemical composition and NiAl alloys doped with Cr, Zr, Fe and Mg. The results indicate that in B2-NiAl and Ll2-Ni3Al alloys, some of the valance electrons of Ni and Al atoms are localized, which leads to a lower free electron density of the alloy. The mean free electron density of the binary Ni-Al alloy decreases with increasing Al content. The open volume of defects on grain boundary of the Ni1Al is larger than that of monovacancy or dislocation. Structural vacancies and microvoids are found in B2-NiAl alloys with Al content above 45%(mole fraction), and the concentration of the vacancies and open volume of microvoids will increase with higher Al content. The addition of Cr, Zr and Fe into a NiAl alloy can increase its mean free electron density and reduce the open volume o f defects on its grain boundary, while with addition of Mg into the NiAl alloy, its mean free electron density decreases and open volume of boundary defects increases.
附件: yw2002-03-03
附件: yw2002-03-03
Key words: Ni-Al alloy; chemical composition; alloying element; microdefect; electron density