The effects of Al, Cr and Sn on segregation, microstructure, phase stability and hardness of Nb-24Ti-18Si-5X (X = Al, Cr, Sn, at%) alloys were studied. The microstructure of the as cast alloys with Cr, Al and Sn respectively contained (Nb,Ti)ss, Nb3Si, αNb5Si3 and C14-NbCr2 Laves, (Nb,Ti)ss and βNb5Si3 and (Nb,Ti)ss, Nb3Sn and Nb5Si3. The microstructures of the heat treated alloys with Al and Cr (1500
C/100 h) contained (Nb,Ti)ss and αNb5Si3 and the alloy with Sn (1200
C/100 h) contained (Nb,Ti)ss, Nb3Sn and αNb5Si3. Compared with Al and Cr, alloying with Sn enhanced the stability of the as cast microstructure, caused strong macrosegregation of Si and Ti, suppressed the segregation of Ti in the (Nb,Ti)ss that was promoted by Al and Cr, had the strongest effect on the macrohardness of the cast and heat treated alloys and on the vol% of the Nbss. All three alloying additions promoted the transformation of βNb5Si3 to αNb5Si3 during heat treatment and decreased the hardness of Nb5Si3 in the as cast alloys with Sn having the strongest effect and Al the weakest. After the heat treatment the hardness of Nb5Si3 increased in the alloys containing Cr and Sn and decreased in the Al containing alloy with Cr having the strongest effect.