PROCESS FOR MAKING TI-NI BASED FUNCTIONALLY GRADED ALLOYS AND TI-NI BASED FUNCTIONALLY GRADED ALLOYS PRODUCED THEREBY
The present invention relates to Ti—Ni based functionally graded alloys easy in proportional control, which are made by cold working and annealing Ti—Ni based alloys under a predetermined temperature gradient. The thus processed Ti—Ni based functionally graded alloys have a shape memory effect and an ultra elasticity and at the same time, have a consecutive variation of shape depending on a temperature variation.
The present invention relates to Ti—Ni based functionally graded alloys, and more particularly, to a process for making Ti—Ni based functionally graded alloys and Ti—Ni based functionally graded alloys produced thereby, in which Ti—Ni based alloys are cold worked, annealed under a predetermined temperature gradient, and functionally graded.
BACKGROUND ARTTi—Ni based shape memory alloys are rapidly deformed at a Martensite transformation start temperature (Ms) if being cold worked, annealed at a predetermined temperature, and cooled with being given a load. After that, if a temperature elevates, a recovery of rapid deformation occurs at an austenite deformation start temperature (As) (Referring to
In case where the Ti—Ni based shape memory alloys are applied as an actuator element for robot, they have to enable a position control by proportional control. However, because the conventional Ti—Ni based shape memory alloys are rapidly deformed at a specific temperature, they were appropriate for an on-off switching actuator, but were inappropriate for a proportional control actuator.
The present invention is a result of making efforts to fix the defects in which the shape memory alloys are rapidly deformed at a specific temperature.
DISCLOSURE OF INVENTION Technical ProblemAccordingly, the present invention is directed to a process for making Ti—Ni based functionally graded alloys and Ti—Ni based functionally graded alloys produced thereby that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a process for making Ti—Ni based functionally graded alloys, for facilitating a proportional control by consecutively varying a transformation temperature (Ms and As) within the same Ti—Ni based alloys and generating gradual deformation over a wide range of temperature (Referring to
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, there is provided a process for making Ti—Ni based functionally graded alloys, wherein Ti—Ni based alloys are cold worked, annealed under a temperature gradient, and given functionally grading.
Cold working may be performed by 25% to 65% and annealing may be performed under a temperature gradient of 823 K to 466 K.
In another aspect, there is provided Ti—Ni based functionally graded alloys enabling a proportional control, made according to the process.
A deformation-rate recovery speed of the alloys may be reduced to 1/30 to 1/100.
Advantageous EffectsTi—Ni based alloys processed according to the present invention has a shape memory effect and an ultra elasticity and at the same time, a deformation-rate recovery speed gets smaller 1/30 to 1/100 compared to that of conventional alloys. The Ti—Ni based alloys having a low deformation-rate recovery speed is easy in position control through proportional control.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to accompanying drawings.
First Exemplary EmbodimentTi-50.0Ni (at %) alloys were cold worked within a range of 25% to 65% before being heat-treated under a temperature gradient. This is because if cold working is performed at less than 25%, a characteristic of functionally grading cannot be obtained due to a small variation of temperature after heat treatment and cold working of more than 65% is impossible. The temperature gradient heat treatment was performed using a heat treatment furnace having a temperature gradient of 823 K to 466 K. However, in the case of 65% cold working, a heat treatment was performed at a temperature gradient of 823 K to 658 K. This is because if a heat treatment is performed at a temperature gradient of 658 K to 466 K, a deformation ratio is small less than 1% and thus is inappropriate for an actuator element.
In an exemplary embodiment of the present invention, Ti-50.0Ni (at %) alloys were used as Ti—Ni based alloys. However, in addition, other Ti—Ni based alloys can be also used and even in such a case, a similar result can be obtained.
Mode for the Invention Second Exemplary EmbodimentTi-50.0Ni (at %) alloy wire having a length of 150 mm is 25% cold worked and annealed under a temperature gradient of 658 K to 466 K. A sample was taken at an interval of 5 mm and processed by differential scanning thermal analysis. A result of arrangement of measured Ms was shown in
Ti-50.0Ni (at %) alloy wire having a length of 150 mm is 25% cold worked and annealed under a temperature gradient of 823 K to 658 K. A sample was taken at an interval of 5 mm and processed by differential scanning thermal analysis. A result of arrangement of measured Ms was shown in
Ti-50.0Ni (at %) alloy wire having a length of 150 mm is 65% cold worked and annealed under a temperature gradient of 823 K to 658 K. A sample was taken at an interval of 5 mm and processed by differential scanning thermal analysis. A result of arrangement of measured Ms was shown in
As described above, it could be confirmed from the exemplary embodiments 2 to 4 and
A deformation (e)-temperature (T) curve for Ti-50.0Ni (at %) alloys processed by solution heat treatment was shown in
Ti-50.0 (at %) alloy wire was 25% cold worked and annealed under a temperature gradient of 658 K to 466 K. A deformation (ε)-temperature (T) curve of the processed wire was shown in
Ti-50.0 (at %) alloy wire was 65% cold worked and annealed under a temperature gradient of 658 K to 466 K. A deformation (ε)-temperature (T) curve of the processed wire was shown in
As described above, it can be appreciated from the exemplary embodiments 5 to 7 and
Ti—Ni based alloys processed according to the present invention has a shape memory effect and an ultra elasticity and at the same time, a deformation-rate recovery speed gets smaller 1/30 to 1/100 compared to that of conventional alloys. The Ti—Ni based alloys having a low deformation-rate recovery speed is easy in position control through proportional control and therefore, is useful for an industrial field requiring a precise position control such as an actuator for robot.
While the present invention has been described and illustrated herein with reference to the preferred embodiments thereof, it will be apparent to those skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of the appended claims and their equivalents.
Claims
1. A process for making Ti—Ni based functionally graded alloys, wherein Ti—Ni based alloys are cold worked, annealed under a temperature gradient, and given functionally grading.
2. The process of claim 1, wherein cold working is performed by 25% to 65% and annealing is performed under a temperature gradient of 823 K to 466 K.
3. Ti—Ni based functionally graded alloys enabling a proportional control, made according to the process of claim 1.
4. The alloys of claim 3, wherein a deformation-rate recovery speed of the alloys is reduced to 1/30 to 1/100.
5. Ti—Ni based functionally graded alloys enabling a proportional control, made according to the process of claim 2.
Type: Application
Filed: Jul 25, 2006
Publication Date: Mar 19, 2009
Inventors: Tae-Hyun Nam (Jinju-si), Ki-Won Kim (Jinju-si), Hyo-Jun Ahn (Jinju-si), Kwon-Koo Cho (Jinju-si), Jou-Hyeon Ahn (Jinju-si), Gyu-Bong Cho (Jinju-si), Yinong Liu (Nedlands), Jung-Moo Lee (Changwon-si), Yun-Jung Lee (Daegu), Cheol-Am Yu (Tongyeong-si)
Application Number: 12/299,113
International Classification: C22F 1/00 (20060101); C22C 28/00 (20060101);