Ni-Ti-Cu shape memory alloy electrothermal actuator element

Abstract

An Ni—Ti—Cu shape memory alloy electrothermal actuator element that recovers its original shape by electrical heating, having a wire diameter of 0.5 mm or less, comprising an Ni—Ti—Cu shape memory alloy wire which contains 49.0 to 51.0 at % of Ti, and 5.0 to 12.0 at % of Cu, with the balance being made of Ni, wherein the actuator element has a deterioration rate of shape strain recovery of 0.5% or less after repeating desired times of shape recovery movement.

What is claimed is:  
     
         1 . An Ni—Ti—Cu shape memory alloy electrothermal actuator element that recovers its original shape by electrical heating, having a wire diameter of 0.5 mm or less, comprising an Ni—Ti—Cu shape memory alloy wire which contains 49.0 to 51.0 at % of Ti, and 5.0 to 12.0 at % of Cu, with the balance being made of Ni, wherein the actuator element has a deterioration rate of shape strain recovery of 0.5% or less after repeating desired times of shape recovery movement.  
     
     
         2 . The Ni—Ti—Cu shape memory alloy electrothermal actuator element as claimed in  claim 1 , wherein the Cu content of the Ni—Ti—Cu shape memory alloy is 6.0 to 8.0 at %.  
     
     
         3 . The Ni—Ti—Cu shape memory alloy electrothermal actuator element as claimed in  claim 1 , wherein the Ni—Ti—Cu shape memory alloy wire is heat-treated to achieve memorization of its original shape at a temperature in the range from 400 to 600° C.  
     
     
         4 . The Ni—Ti—Cu shape memory alloy electrothermal actuator element as claimed in  claim 2 , wherein the Ni—Ti—Cu shape memory alloy wire is heat-treated to achieve memorization of its original shape at a temperature in the range from 400 to 600° C.  
     
     
         5 . An Ni—Ti—Cu shape memory alloy electrothermal actuator element, wherein the wire in the actuator element as claimed in  claim 1  is subjected to repeating cycles of heating to a temperature of Af or higher with applying a weight load corresponding to 10 to 30% of a breaking load of the wire, and cooling to a temperature of Mf (a finishing temperature of Martensitic transformation) or lower, and wherein the deterioration rate of shape strain recovery after repeating desired times of shape recovery movement is 0.2% or less.  
     
     
         6 . An Ni—Ti—Cu shape memory alloy electrothermal actuator element, wherein the wire in the actuator element as claimed in  claim 2  is subjected to repeating cycles of heating to a temperature of Af or higher with applying a weight load corresponding to 10 to 30% of a breaking load of the wire, and cooling to a temperature of Mf or lower, and wherein the deterioration rate of shape strain recovery after repeating desired times of shape recovery movement is 0.2% or less.  
     
     
         7 . An Ni—Ti—Cu shape memory alloy electrothermal actuator element, wherein the wire in the actuator element as claimed in  claim 3  is subjected to repeating cycles of heating to a temperature of Af or higher with applying a weight load corresponding to 10 to 30% of a breaking load of the wire, and cooling to a temperature of Mf or lower, and wherein the deterioration rate of shape strain recovery after repeating desired times of shape recovery movement is 0.2% or less.  
     
     
         8 . An Ni—Ti—Cu shape memory alloy electrothermal actuator element, wherein the wire in the actuator element as claimed in  claim 4  is subjected to repeating cycles of heating to a temperature of Af or higher with applying a weight load corresponding to 10 to 30% of a breaking load of the wire, and cooling to a temperature of Mf or lower, and wherein the deterioration rate of shape strain recovery after repeating desired times of shape recovery movement is 0.2% or less.