Influence of chemical composition and alloying elements on microdefects and electron densityin Ni-Al alloys

来源期刊：中国有色金属学报(英文版)2002年第3期

论文作者：邓文 黄宇阳 吴道宏 熊良钺 王淑荷 郭建亭

文章页码：370 - 374

Key words：Ni-Al alloy; chemical composition; alloying element; microdefect; electron density

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.