Method of thermo-mechanical-treatment for fe-mn-si shape-memory alloy doped with nbc

Abstract

The present invention provides a thermomechanical treatment means for a Fe—Mn—Si-based shape memory alloy having specified components with Nb, C addition with simple deformation prior to aging. Such deformation treatment prior to aging is carried out in the inventions of the prior applications in a temperature range of from 500° C. to 800° C. According to the present invention, however, the deformation treatment prior to the aging treatment can be successfully carried out not at high temperature but at room temperature, if the deformation ratio is in a specified range. The technical meaning of the present invention must be clearly understood as compared to the prior art and the inventions of the prior applications because the present invention allows the treatment at room temperature while the others require troublesome treatment at high temperature so that there is significant difference therebetween. That is, according to the present invention, the remarkable improvement in shape memory property is achieved first time by a combination of specified alloy components, specified deformation ratio at room temperature, and setting of aging condition to a certain range. With the development of the present invention, it is expected that the use of shape memory alloys will be accelerated toward the practical use in a wide variety of fields.

1 . A thermomechanical treatment method for a Fe—Mn—Si-based shape memory alloy with Nb, C addition comprising: 
 deforming a Fe—Mn—Si-based shape memory alloy with Nb, C addition by a deformation ratio of from 5% to 40% at room temperature, and    subjecting the deformed alloy to aging heating treatment to precipitate NbC carbides.    
   
   
       2 . A thermomechanical treatment method for a Fe—Mn—Si-based shape memory alloy with Nb, C addition as claimed in  claim 1 , wherein the Fe—Mn—Si-based shape memory alloy with Nb, C addition comprises, as alloy components, Mn: 15% to 40% by weight, Si: 3% to 15% by weight, Nb: 0.1% to 1.5% by weight, C: 0.01% to 0.2% by weight, and Fe and inevitable impurities: residual amount, wherein the atomic ratio Nb/C between Nb and C is 1 or more.  
   
   
       3 . A thermomechanical treatment method for a Fe—Mn—Si-based shape memory alloy with Nb, C addition as claimed in  claim 1 , wherein the Fe—Mn—Si-based shape memory alloy with Nb, C addition comprises, as alloy components, Mn: 15% to 40% by weight, Si: 3% to 15% by weight, Cr: 1% to 20% by weight, Nb: 0.1% to 1.5% by weight, C: 0.01% to 0.2% by weight, and Fe and inevitable impurities: residual amount, wherein the atomic ratio Nb/C between Nb and C is 1 or more.  
   
   
       4 . A thermomechanical treatment method for a Fe—Mn—Si-based shape memory alloy with Nb, C addition as claimed in  claim 1 , wherein the Fe—Mn—Si-based shape memory alloy with Nb, C addition comprises, as alloy components, Mn: 15% to 40% by weight, Si: 3% to 15% by weight, Cr: 1% to 20% by weight, Ni: 0.1% to 20% by weight, Nb: 0.1% to 1.5% by weight, C: 0.01% to 0.2% by weight, and Fe and inevitable impurities: residual amount, wherein the atomic ratio Nb/C between Nb and C is 1 or more.  
   
   
       5 . A thermomechanical treatment method for a Fe—Mn—Si-based shape memory alloy with Nb, C addition as claimed in any one of claims  2  through  4 , wherein the atomic ratio between Nb and C is set in a range of from 1.0 to 1.2.  
   
   
       6 . A thermomechanical treatment method for a Fe—Mn—Si-based shape memory alloy with Nb, C addition as claimed in any one of claims  2  through  4 , wherein the Fe—Mn—Si-based shape memory alloy with Nb, C addition contains, as impurities, Cu: 3% by weight or less, Mo: 2% by weight or less, Al: 10% by weight or less, Co: 30% by weight or less, and/or N: 5000 ppm or less.  
   
   
       7 . A thermomechanical treatment method for a Fe—Mn—Si-based shape memory alloy with Nb, C addition as claimed in any one of claims  1  through  4 , wherein the conditions for the aging heating treatment are a temperature range of 400° C. to 1000° C. and a time period from 1 minute to 2 hours.