ROOM-TEMPERATURE PHASES OBSERVED IN TI53-XNI47ZRX HIGH-TEMPERATURE SHAPE-MEMORY ALLOYS

Ti53-xNi47Zrx (x=5 similar to 20 at%) shape memory alloys exhibit mart ensitic transformation characteristics and their transformation temper atures increase linearly with increasing Zr content. There are three d ifferent phases observed in 900 degrees C homogenized alloys for Zr co ntent greater than or equal to 10 at%, including the grey (Ti,Zr)Ni ma trix, the black (Ti,Zr)(2)Ni particles and the white lambda(1) phase. But only the former two phases are found in the Ti48Ni47Zr5 alloy. DTA test results show that the homogenized Ti38Ni47Zr15 alloy has three e ndothermic peaks in the thermograph, in which the 930 degrees C endoth ermic peak is associated with the solid<->liquid transition of lambda( 1) phase, the peak at 990 degrees C is associated with the reverse per itectic transformation of (Ti,Zr)(2)Ni->(Ti,Zr)Ni+liquid and the one a t 1160 degrees C is the dissolution reaction of the (Ti,Zr)Ni->liquid. (C) 1998 Elsevier Science S.A.