Abstract: The solid solubilities of 15 common alloying elements added to the Ll_2-type intermetallic compound Ni_3Si at 900°C have been estimated,and their substitution modes have been de- duced from the direction of solubility lobe of the compound.It is shown that the alloying behaviours in Ni_3Si are determined by both size and electronic factors,i.e.,the substitution mode is governed by electronic configuration and solubility by the both.An interaction parameter is presented to describe quantitatively the influence of electronic configuration on substitution mode and the solubility limit can be successfully explained together with atom radius.

Key words: alloying behaviour, atom size, electronic configuration, interaction parameter