中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
Vol. 7 No. 1 March 1997 |
(Shanghai Jiaotong University; Shanghai 200030)
Abstract:To further understand the alloying behavior for Ni3Al, the alloying behavior of boron and carbon in Ni 3Al has been studied by X ray powder diffraction analysis. The results show that boron and carbon occupy the octahedral interstitial site with six nearest neighboring nickel atoms in the L12 type structure, and the additives can increase the degree of long range order for Ni 3Al, the degree of long range order for Ni 3Al varies with the stoichiometry; the effects of boron and carbon on the lattice parameter of Ni 3Al are also evaluated. Comparatively, the degree of the long range order is highest for Al rich Ni 74 Al 26 and it is lowest for Ni rich Ni 76 Al 24 . The order degree for stoichiometric Ni 75 Al 25 stands between them. Furthermore, the role of boron in increasing the degree of long range order is more significant in Al rich Ni 74 Al 26 than in Ni rich Ni 76 Al 24 or stoichiometric Ni 75 Al 25 . With boron and carbon content increasing, the lattice parameter of Ni 3Al increases linearly, and the increment caused by carbon is more pronounced than that by boron. Moreover, the increasing trend of the lattice parameter by boron addition is followed by the stoichiometric sequence of Ni 76 Al 24, Ni 75 Al 25, Ni 74 Al 26 .
Key words: intermetallics Ni 3Al stoichiometry solid solution alloying lattice parameter