Shape memory properties of the Ti36Ni49Hf15 high temperature shape memory alloy

The shape memory properties have been studied in a Ti36Ni49Hf15 high temper ature shape memory alloy (SMA) by bending tests. The shape memory effect (S ME) of the alloy is closely related to the deformation condition. It shows about 3% completely reversible strain when the TiNiHf alloy is deformed at the room temperature. The shape recovery ratio is constant at 92% when the deformation temperature is below 457 K, then rapidly decreases to zero abov e 590 K for the specimen deformed to 4.5%. Obvious two-way shape memory eff ect (TWSME) is obtained in the Ti36Ni49Hf15 alloy aged at 973 K for various hours. As the aging time further increases, the TWSME decreases. Moreover, TWSME in the aged Ti36Ni49Hf15 alloy is unstable and decreases rapidly aft er several thermal cycles. (C) 2000 Elsevier Science B.V. All rights reserv ed.