ELECTRON CONCENTRATION RULE FOR THE FORMATION OF Ti_3X PHASE

Based on our previous works,four ternary alloy systems,Ti-Al-Ge,Ti-Al-In,Ti-Al-Hf and Ti-Al-Ta,were selected to investigate the electron concentrationrule for the formation of Ti_3X-phase.Results show that the formation of Ti_3X-phase in theTi-Al solid solution containing Ge,In,Hf and Ta obeys the electron concentration rule aswell.The characteristic electron concentration for the formation of Ti_3X-phase is(?)=∑ N_if_i=2.12.The valence electron number of the alloying elements depends on their ownelectronic structure,i.e.,N_(Ge)=4(s~2p~2),N_(In)=3(s~2p~1)for non-transition elements Ge and In;N_(Hf)=N_(Ta)=2 for transition elements Hf and Ta.