Patent ID: 7955449

Claim:
A process for treating a device formed of nickel-titanium based alloy having an A f temperature in the range of between about 25° C.-35° C., and a T R temperature in the range of between about 5° C.-25° C., said device exhibiting a one-way shape memory effect in which it spontaneously transforms from an initial shape in the austenitic phase to a final shape in the R-phase, so that the device exhibits a two-way shape memory effect (TWSME) based on a reversible R-phase transformation, comprising the steps of: (a) loading said device at a temperature in a range T 1 , wherein T R <T 1 <A f +30° C.; (b) cooling said device in its loaded condition to a temperature in a range T 2 , wherein T R −30° C.<T 2 <T R ; (c) unloading said device at a temperature in the range T 2 ; (d) thermocycling said unloaded device several times, wherein each thermocycle includes, (1) heating said unloaded device to a temperature in a range T 3 , wherein A f <T 3 <A f +30° C.; and (2) cooling said unloaded device to a temperature in the range T 2 .