Precipitation-strengthened shape memory alloys, designing methods and applications of same

Abstract

The invention relates to a method for producing a precipitation-strengthened shape memory alloy (SMA), comprising providing a composition designed according to property objectives of the precipitation-strengthened SMA, wherein the property objectives are design specifications of the precipitation-strengthened SMA; performing homogenization and solution treatment of the composition at a first temperature for a first period of time followed by water quenching to form an ingot; and aging treatment of the ingot at a second temperature for a second period of time followed by water quenching to form the precipitation-strengthened SMA.

What is claimed is: 
     
         1 . A method for producing a precipitation-strengthened shape memory alloy (SMA), comprising:
 providing a composition designed according to property objectives of the precipitation-strengthened SMA, wherein the property objectives are design specifications of the precipitation-strengthened SMA;   performing homogenization and solution treatment of the composition at a first temperature for a first period of time followed by water quenching to form an ingot; and   aging treatment of the ingot at a second temperature for a second period of time followed by water quenching to form the precipitation-strengthened SMA.   
     
     
         2 . The method of  claim 1 , wherein the first temperature is in a range of about 840-1260° C., the first period of time is in a range of about 58-86 h, the second temperature is in a range of about 480-720° C., and the second period of time is in a range of about 8-12 h. 
     
     
         3 . The method of  claim 2 , wherein the first temperature is about 1050° C., the first period of time is about 72 h, the second temperature is about 600° C., and the second period of time is about 10 h. 
     
     
         4 . The method of  claim 1 , wherein the property objectives comprises comprising a yield strength being more than about 1500 MPa at room temperature, a transformation temperature in a range of about −15 to 20° C., a misfit in a range of about 0.9-1.1%. 
     
     
         5 . The method of  claim 1 , wherein the composition comprises Ni in about 50 at. %, Ti in a range of about 23.6-24.2 at. %, Hf in a range of about 21.8-22 at. % and Al in a range of about 4-4.4 at. %, wherein the precipitation-strengthened SMA comprises an Ni 50 Ti 23.6 Hf 21.8-22 Al 4-4.4  alloy. 
     
     
         6 . A method for designing a precipitation-strengthened shape memory alloy (SMA), comprising:
 defining property objectives of the precipitation-strengthened SMA, wherein the property objectives are design specifications of the precipitation-strengthened SMA;   designing a composition of the precipitation-strengthened SMA according to the property objectives; and   processing the composition to form the precipitation-strengthened SMA that meets the property objectives.   
     
     
         7 . The method of  claim 6 , wherein the processing step comprises
 performing homogenization and solution treatment of the composition at a first temperature for a first period of time followed by water quenching to form an ingot; and   aging treatment of the ingot at a second temperature for a second period of time followed by water quenching to form the precipitation-strengthened SMA.   
     
     
         8 . The method of  claim 7  wherein the first temperature is in a range of about 840-1260° C., the first period of time is in a range of about 58-86 h, the second temperature is in a range of about 480-720°° C., and the second period of time is in a range of about 8-12 h. 
     
     
         9 . The method of  claim 8 , wherein the first temperature is about 1050° C., the first period of time is about 72 h, the second temperature is about 600° C., and the second period of time is about 10 h. 
     
     
         10 . The method of  claim 7 , wherein the property objectives comprises comprising a yield strength being more than about 1500 MPa at room temperature, a transformation temperature in a range of about −15 to 20° C., a misfit in a range of about 0.9-1.1%. 
     
     
         11 . The method of  claim 7 , wherein the composition comprises Ni in about 50 at. %, Ti in a range of about 23.6-24.2 at. %, Hf in a range of about 21.8-22 at. % and Al in a range of about 4-4.4 at. %, wherein the precipitation-strengthened SMA comprises an Ni 50 Ti 23.6 Hf 21.8-22 Al 4-4.4  alloy.