SITE OCCUPANCY OF ALLOYING ELEMENTS IN TINI COMPOUNDS

A method is proposed on the basis of electronic structure calculations to predict the substitution behaviour of alloying elements in TiNi co mpounds. The electronic structures of 36 elements occupying both Ti an d Ni sites in TiNi are calculated using the discrete variational-X(alp ha) cluster method. A diagram is drawn using Bo(Ti), and Bo(Ni), the t otal bond orders between the alloying elements and surrounding atoms. Two lines on the diagram separate the alloying elements into three gro ups. The elements located outside the two lines occupy either Ti or Ni sites regardless of the composition. The substitution behaviour of el ements in between are affected by the alloy composition. The effects o f composition, multielement alloying and ordering time and the influen ce of entropy are discussed. The results agree well with experiments.