- Email: [email protected]
Internal friction of TiNi alloys produced by a lamination process
Journal of Alloys and Compounds 333 (2002) 159–164
L
www.elsevier.com / locate / jallcom
Internal friction of TiNi alloys produced by a lamination process a, b b a a a K. Hishitani *, M. Sasaki , D. Imai , Y. Kogo , N. Urahashi , N. Igata a
b
Science University of Tokyo, 2641 Yamazaki Noda, Chiba 278 -8510, Japan Nippon Metal Industry, 1 -30 Ohyatna, Sagamihara, Kanagawa 229 -1184, Japan
Received 14 February 2001; received in revised form 8 May 2001; accepted 8 June 2001
Abstract Recently, the demand for higher damping materials with higher strength has been requested from the precision machine industries. Of these materials, the TiNi alloy has excellent characteristics with high damping capacity and high strength. However, with respect to practical use, its cold rolling is difficult. In order to solve this problem, we examined the production of the TiNi alloy from the Ti–Ni laminated material by the solid-phase diffusion method. In this study, to investigate the best processing conditions to make a high damping TiNi alloy with high strength, the effects of the material composition, annealing time and cooling rate of the water quenching on the internal friction and tensile strength were examined. As a result, a material with an internal friction of d 50.14 at 250 K and ultimate tensile strength about 800 MPa was obtained. 2002 Elsevier Science B.V. All rights reserved. Keywords: Internal friction; High damping; TiNi; Martensitic transformation; Lamination
1. Introduction
2. Experimental
Recently, the demand for the higher damping material with the higher strength has increased with the high integration of technology. Many kinds of high damping materials have already been developed. However, they are not widely used as the industrial materials, because the higher damping material usually has a lower strength. The TiNi alloy has excellent characteristics with respect to high damping capacity and high strength. Since there is a problem with its cold rolling, we examined the method for producing the TiNi alloy from the Ti–Ni laminated material by the solid-phase diffusion method. In this method, the cold work before the thermal diffusion is easy, because the Ti–Ni laminated material is pure metal in each layer. In this paper, the processing of the TiNi alloy from the Ti–Ni laminated material by the solid-phase diffusion method and the effects of the composition, annealing time and cooling rate of the water quenching on the internal friction and tensile strength are reported.
2.1. Materials
*Corresponding author. Tel.: 181-471-24-1501; fax: 181-471-239362. E-mail address: [email protected] (K. Hishitani).
Square titanium (purity, 99.9%) sheets with a thickness of 0.20 mm and nickel (purity, 99.7%) sheets with a thickness of 0.10–0.15 mm were used in this process. These were cleaned before assembly, and then stacked in about 180 layers. The stack was then placed in a steel box. The box was then pumped down to a pressure of 10 22 Pa through a pipe welded to the box. The box was heated in an electric furnace at a temperature of 1123 K for 1.8 ks. This was hot rolled to the extent of a 90% reduction in thickness. After eliminating the surface steel, this plate was cold rolled to the extent of a 70% reduction in thickness. The rolled plate was next cut into small plates and again sealed in the stainless steel case. The case was pumped down to a pressure of 5.0 Pa, and then annealed at 1163 K for 21.6–864 ks and subsequently quenched in water. Specimens were taken out from the stainless steel case, and then annealed again at 773 K for 3.6 ks and cooled in the vacuum image furnace. To eliminate the shape change during the annealing, the specimens were clamped between two flat stainless plates. The compositions of the samples were controlled by changing the thickness and stack number of the Ti and Ni sheets. Table 1 shows the results of the chemical analysis.
0925-8388 / 02 / $ – see front matter 2002 Elsevier Science B.V. All rights reserved. PII: S0925-8388( 01 )01718-2
K. Hishitani et al. / Journal of Alloys and Compounds 333 (2002) 159 – 164
160 Table 1 Results of the chemical analysis Sample no.
T1
T2
TN
N1
N2
Composition
Ti–46.1 at.%Ni
Ti–48.5 at.%Ni
Ti–50.0 at.%Ni
Ti–52.6 at.%Ni
Ti–54.4 at.%Ni
Ti-rich and Ni-rich samples are described by Tx and Nx, respectively, and the equiatomic sample is described by TN. In order to examine the effect of the cooling rate during the water quenching after annealing, the sample TN was directly quenched into water after taking it out from the case after annealing at 1163 K for 260 ks. This sample is described as the rapid water quenched (RWQ) specimen and the sample quenched with the stainless case is described as the water quenched (WQ) specimen.
2.2. Measurements Measurements of the temperature dependence of the internal friction and the Young’s modulus were carried out using the transverse vibration method (Ulvac IFT-1500Y). The internal friction, d, was deduced from the decay of the free oscillations of the specimen. The size of the specimen was 12031030.6 mm 3 and the measuring frequency was about 150 Hz at room temperature. Measurements were carried out at the strain amplitude of about 7310 26 . During the measurements, the samples were first quickly heated to 400 K and then cooled to 150 K at a cooling rate of 3.3310 22 K / s. When the preset temperature (150 K) was reached, the specimens were again heated to 400 K at the same rate. Tensile tests were carried out using an Instron-type testing machine at room temperature. The crosshead speed was 1.7310 23 mm / s. In order to investigate the other properties of this material, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurement and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations were carried out.
Fig. 1. Temperature dependence of the internal friction and Young’s modulus of T 1 (d), T 2 (3), TN (m), N 1 (j) and N 2 (1) samples annealed for 260 ks on heating measurement.
internal friction peak was observed at around 250 K. In the Ni-rich samples, and N 2 , the decrease in the internal friction corresponding to a Young’s modulus minimum was observed at around 290 K. A large internal friction peak was observed at around 230 K. Fig. 2 shows the DSC curves of the T 1 , TN, and samples
3. Results and discussion
3.1. Internal friction and Young’ s modulus 3.1.1. Effect of composition Fig. 1 shows the temperature dependence of the internal friction and Young’s modulus of the T 1 , T 2 , TN, N 1 and N 2 samples annealed at 1163 K for 260 ks on the heating measurement. In the Ti-rich samples, T 1 and T 2 , the rapid decrease in the internal friction corresponding to a minimal Young’s modulus was observed at around 320 K. In the TN sample, the decrease in the internal friction corresponding to the broad minimum of Young’s modulus was observed in the temperature range 250–350 K. A large
Fig. 2. DSC results of T 1 , TN and N 1 samples annealed at 1163 K for 260 ks.
K. Hishitani et al. / Journal of Alloys and Compounds 333 (2002) 159 – 164
Fig. 3. Relaxation peaks in TiNi alloys.
annealed at 1163 K for 260 ks. The exothermic peak during cooling is due to the transformation from austenite to martensite, while the endothermic peak during heating is due to the transformation from martensite to austenite. The decrease in the internal friction and the Young’s modulus minimum corresponded to the DSC peaks in each sample. Therefore, the change in the internal friction and modulus seems to be dependent on the transformation from martensite to austenite. The large peaks, observed in the TN, N 1 and N 2 samples from 230 to 250 K did not correspond to the DSC peaks, and are not due to transformation. This peak might be due to thermally activated relaxation process, because it was observed at the same temperature during cooling and heating measurements.
161
Several types of relaxation peaks have been reported. Hasiguti and Igata [1] report a Bordoni type peak and point defect-dislocation interaction peaks in Ti and Ni. For TiNi, Hsiguti and Iwasaki [2] report a peak at 203 K with an activation energy of 0.38 eV and a frequency factor of 6310 9 s 21 . This might be due to a movement of dislocation or a movement of point-defect-pinned dislocations. Postnikow et al. [3] and Zhu et al. [4] also reported a peak of the same mechanism. Tirbonod and Koshimizu [5] reported a Bordoni type peak in an equiatomic TiNi alloy. The presence of this peak should be due to the motion of imperfect dislocations with a Burgers vector smaller than the lattice parameter. Coluzzi et al. [6] reported a frequency insensitive peak probably due to thermomechanical depinning of twin boundaries from point defects. Fig. 3 shows the Arrhenius plot for relaxation peaks of experimental results and present data. Curves A and B were also plotted from present data [2,5]. Experimental results agreed well with the curve A. Therefore, the observed relaxation peak might be due to a movement of dislocation or a movement of point-defect-pinned dislocations. Fig. 4 shows the diffraction patterns of the T 1 , T 2 , TN, N 1 and N 2 samples annealed at 1163 K for 260 ks (CuKa). A very broad TiNi line was observed in all these specimens. Patterns of Ti 2 Ni and TiNi 3 increased with the increase in the Ti and Ni contents, respectively. Fig. 5 is a TEM micrograph of the T 2 sample annealed at 1163 K for 260 ks. Many precipitates were observed at the interface of the martensite twins, although few precipitates were observed in the TN sample. From these facts, the effect of the Ti 2 Ni precipitation is considered as one of the reasons why the peak did not appear in the Ti-rich samples. In the temperature range .300 K, the Ti-rich samples showed a higher damping capacity. This is based on the fact that the transformation temperature is higher in Ti-rich samples. In the temperature range ,300 K, the TN sample shows a higher damping capacity due to the effect of the relaxation peak.
Fig. 4. Diffraction pattern of T 1 , T 2 , TN, N 1 and N 2 samples annealed at 1163 K for 260 ks. CuKa radiation; d, TiNi; ., Ti 2 Ni; m, TiNi 3 .
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K. Hishitani et al. / Journal of Alloys and Compounds 333 (2002) 159 – 164
Fig. 5. TEM micrograph of the T 2 sample annealed at 1163 K for 260 ks.
Fig. 7. DSC results of TN samples annealed at 1163 K for 21.6, 64.8 and 260 ks.
3.1.2. Effect of annealing time Fig. 6 shows the temperature dependence of the internal friction and Young’s modulus of the TN sample annealed at 1163 K for 21.6, 64.8 and 260 ks on the heating measurement. Decreases in the internal friction and Young’s modulus with austenite transformation were observed in all the samples. Fig. 7 shows the DSC curves of the TN sample annealed at 1163 K for 21.6, 64.8 and 260 ks. In the samples annealed for 21.6 and 64.8 ks, two peaks were observed in each of the cooling and heating runs. This shows that Ti- and Ni-rich areas exist in the material. In the sample annealed for 64.8 ks, a high damping capacity was observed in a wide temperature range. This might be due to the coexistence of the Ti- and
3.1.3. Effect of cooling rate Fig. 8 shows the temperature dependence of the internal friction and Young’s modulus of the WQ and RWQ specimens. The relaxation peak of the RWQ specimen was higher than that of the WQ specimen. Fig. 9 is TEM micrographs of the WQ and RWQ specimen. Compared with the WQ specimen, very fine martensite twins were
Fig. 6. Temperature dependency of the internal friction and Young’s modulus of TN samples annealed at 1163 K for 21.6 (d), 64.8 (m) and 260 ks (3) on heating measurement.
Fig. 8. Temperature dependency of the internal friction and Young’s modulus of WQ (3) and RWQ (d) specimens on heating measurements.
Ni-rich areas. When the TiNi alloy is produced by the lamination process, by controlling the ratio of the Ti- and Ni-rich areas by the annealing time, it is possible to obtain the damping effect by the transformation over a wide temperature range.
K. Hishitani et al. / Journal of Alloys and Compounds 333 (2002) 159 – 164
163
Fig. 11. Ultimate tensile strength of TN samples annealed at 1163 K for 21.6–864 ks.
3.2. Ultimate tensile strength
Fig. 9. TEM micrographs of TN samples at 1163 K for 260 ks; (a) WQ, (b) RWQ.
observed in the RWQ specimen. It is considered that this phenomenon is caused by the effect of the rapid cooling. The refinement of the martensite twins may be the reason of the heightened relaxation peak [7].
Fig. 10. Ultimate tensile strength of T 1 , T 2 , TN, N 1 and N 2 samples annealed at 1163 K for 260 ks.
Fig. 10 shows the ultimate tensile strength of the T 1 , T 2 , TN, N 1 and N 2 samples annealed at 1163 K for 260 ks. The ultimate tensile strength increased with the increase in the Ni content. Fig. 11 shows the ultimate tensile strength of the TN sample annealed at 1163 K for 21.6–864 ks. The tensile strength increased with the increase in the annealing time. These results show that the tensile strength can be controlled by the composition and the annealing time. Fig. 12 shows SEM micrographs of the TN sample annealed at 1163 K for 21.6 and 260 ks. Many voids were observed in each sample due to the Kirkendall effect. The Ti-rich layers were observed in the sample annealed for 21.6 ks. Based on the results of the XRD measurements and point analysis, this layer is estimated to be Ti 2 Ni in the Ti-rich samples annealed for 260 ks and the TN sample annealed for a shorter time, the Ti 2 Ni layers were also observed. From this fact, the effect of the Ti 2 Ni layer was considered as the origin of that these samples showed the lower tensile strength.
Fig. 12. SEM micrographs of TN samples annealed at 1163 K for 21.6 ks (a) 260 ks (b).
164
K. Hishitani et al. / Journal of Alloys and Compounds 333 (2002) 159 – 164
4. Summary In this paper, the processing of the TiNi alloy from the Ti–Ni laminated material by the solid-phase diffusion method and the effects of the composition, annealing time and cooling rate of the water quenching on the internal friction and tensile strength are reported. The main results are as follows 1. It was possible to produce the TiNi alloy from the Ti–Ni laminated material by the solid-phase diffusion method. 2. In the temperature range .300 K, the Ti-rich samples show a higher damping capacity. This value is higher in the Ti-rich samples due to the transformation temperature. In the temperature range ,300 K, the TN sample shows a higher damping capacity due to the effect of the relaxation peak, and this peak might be due to a movement of dislocations or a movement of pointdefect-pinned dislocations. 3. In the sample annealed for 64.8 ks, a high damping capacity was shown over a wide temperature range. It might be due to the coexistence of the Ti- and Ni-rich areas. When the TiNi alloy is produced by the lamination process, by controlling the ratio of the Ti- and Ni-rich areas by the annealing time, it is possible to obtain the damping effect by the transformation over the wide temperature range.
4. A material with an internal friction of d 50.14 at 250 K and ultimate tensile strength of about 800 MPa was obtained.
Acknowledgements The authors acknowledge the financial support of the Japan Society for the Promotion of Science Research and Development of New High Damping Material Based on Atomistic Design Project and the technical advice of Dr. K. Tsuchiya, Toyohashi University of Technology, who provided the DSC measurements.
References [1] R.R. Hasiguti, N. Igata, G. Kamoshima, Acta Metall. 10 (1962) 442. [2] R.R. Hasiguti, K. Iwasaki, J. Appl. Phys. 59 (1968) 2182. [3] V.S. Postnikov, V.S. Lebedinsky, V.A. Yevsyokov, I.M. Sharskakov, M.S. Pesin, Fiz. Met. Metallov 29 (1970) 34. [4] J.S. Zhu, R. Schaller, W. Benoit, Phys. Lett. A 141 (3,4) (1989) 177–180. [5] B. Tirbond, S. Koshimizu, J. de Phys. 42 (1981) C5–1043. [6] B. Coluzzi, A. Biscarini, R. Campanella, G. Mazzolai, L. Trotta, A. Tuissi, F.M. Mazzolai, Acta Mater. 47 (1999) 1965. [7] Y. Furuya, H. Kimura, T. Masumoto, Mat. Sci. Eng. A181 /A182 (1994) 1076–1080.
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www.elsevier.com / locate / jallcom
Internal friction of TiNi alloys produced by a lamination process a, b b a a a K. Hishitani *, M. Sasaki , D. Imai , Y. Kogo , N. Urahashi , N. Igata a
b
Science University of Tokyo, 2641 Yamazaki Noda, Chiba 278 -8510, Japan Nippon Metal Industry, 1 -30 Ohyatna, Sagamihara, Kanagawa 229 -1184, Japan
Received 14 February 2001; received in revised form 8 May 2001; accepted 8 June 2001
Abstract Recently, the demand for higher damping materials with higher strength has been requested from the precision machine industries. Of these materials, the TiNi alloy has excellent characteristics with high damping capacity and high strength. However, with respect to practical use, its cold rolling is difficult. In order to solve this problem, we examined the production of the TiNi alloy from the Ti–Ni laminated material by the solid-phase diffusion method. In this study, to investigate the best processing conditions to make a high damping TiNi alloy with high strength, the effects of the material composition, annealing time and cooling rate of the water quenching on the internal friction and tensile strength were examined. As a result, a material with an internal friction of d 50.14 at 250 K and ultimate tensile strength about 800 MPa was obtained. 2002 Elsevier Science B.V. All rights reserved. Keywords: Internal friction; High damping; TiNi; Martensitic transformation; Lamination
1. Introduction
2. Experimental
Recently, the demand for the higher damping material with the higher strength has increased with the high integration of technology. Many kinds of high damping materials have already been developed. However, they are not widely used as the industrial materials, because the higher damping material usually has a lower strength. The TiNi alloy has excellent characteristics with respect to high damping capacity and high strength. Since there is a problem with its cold rolling, we examined the method for producing the TiNi alloy from the Ti–Ni laminated material by the solid-phase diffusion method. In this method, the cold work before the thermal diffusion is easy, because the Ti–Ni laminated material is pure metal in each layer. In this paper, the processing of the TiNi alloy from the Ti–Ni laminated material by the solid-phase diffusion method and the effects of the composition, annealing time and cooling rate of the water quenching on the internal friction and tensile strength are reported.
2.1. Materials
*Corresponding author. Tel.: 181-471-24-1501; fax: 181-471-239362. E-mail address: [email protected] (K. Hishitani).
Square titanium (purity, 99.9%) sheets with a thickness of 0.20 mm and nickel (purity, 99.7%) sheets with a thickness of 0.10–0.15 mm were used in this process. These were cleaned before assembly, and then stacked in about 180 layers. The stack was then placed in a steel box. The box was then pumped down to a pressure of 10 22 Pa through a pipe welded to the box. The box was heated in an electric furnace at a temperature of 1123 K for 1.8 ks. This was hot rolled to the extent of a 90% reduction in thickness. After eliminating the surface steel, this plate was cold rolled to the extent of a 70% reduction in thickness. The rolled plate was next cut into small plates and again sealed in the stainless steel case. The case was pumped down to a pressure of 5.0 Pa, and then annealed at 1163 K for 21.6–864 ks and subsequently quenched in water. Specimens were taken out from the stainless steel case, and then annealed again at 773 K for 3.6 ks and cooled in the vacuum image furnace. To eliminate the shape change during the annealing, the specimens were clamped between two flat stainless plates. The compositions of the samples were controlled by changing the thickness and stack number of the Ti and Ni sheets. Table 1 shows the results of the chemical analysis.
0925-8388 / 02 / $ – see front matter 2002 Elsevier Science B.V. All rights reserved. PII: S0925-8388( 01 )01718-2
K. Hishitani et al. / Journal of Alloys and Compounds 333 (2002) 159 – 164
160 Table 1 Results of the chemical analysis Sample no.
T1
T2
TN
N1
N2
Composition
Ti–46.1 at.%Ni
Ti–48.5 at.%Ni
Ti–50.0 at.%Ni
Ti–52.6 at.%Ni
Ti–54.4 at.%Ni
Ti-rich and Ni-rich samples are described by Tx and Nx, respectively, and the equiatomic sample is described by TN. In order to examine the effect of the cooling rate during the water quenching after annealing, the sample TN was directly quenched into water after taking it out from the case after annealing at 1163 K for 260 ks. This sample is described as the rapid water quenched (RWQ) specimen and the sample quenched with the stainless case is described as the water quenched (WQ) specimen.
2.2. Measurements Measurements of the temperature dependence of the internal friction and the Young’s modulus were carried out using the transverse vibration method (Ulvac IFT-1500Y). The internal friction, d, was deduced from the decay of the free oscillations of the specimen. The size of the specimen was 12031030.6 mm 3 and the measuring frequency was about 150 Hz at room temperature. Measurements were carried out at the strain amplitude of about 7310 26 . During the measurements, the samples were first quickly heated to 400 K and then cooled to 150 K at a cooling rate of 3.3310 22 K / s. When the preset temperature (150 K) was reached, the specimens were again heated to 400 K at the same rate. Tensile tests were carried out using an Instron-type testing machine at room temperature. The crosshead speed was 1.7310 23 mm / s. In order to investigate the other properties of this material, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurement and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations were carried out.
Fig. 1. Temperature dependence of the internal friction and Young’s modulus of T 1 (d), T 2 (3), TN (m), N 1 (j) and N 2 (1) samples annealed for 260 ks on heating measurement.
internal friction peak was observed at around 250 K. In the Ni-rich samples, and N 2 , the decrease in the internal friction corresponding to a Young’s modulus minimum was observed at around 290 K. A large internal friction peak was observed at around 230 K. Fig. 2 shows the DSC curves of the T 1 , TN, and samples
3. Results and discussion
3.1. Internal friction and Young’ s modulus 3.1.1. Effect of composition Fig. 1 shows the temperature dependence of the internal friction and Young’s modulus of the T 1 , T 2 , TN, N 1 and N 2 samples annealed at 1163 K for 260 ks on the heating measurement. In the Ti-rich samples, T 1 and T 2 , the rapid decrease in the internal friction corresponding to a minimal Young’s modulus was observed at around 320 K. In the TN sample, the decrease in the internal friction corresponding to the broad minimum of Young’s modulus was observed in the temperature range 250–350 K. A large
Fig. 2. DSC results of T 1 , TN and N 1 samples annealed at 1163 K for 260 ks.
K. Hishitani et al. / Journal of Alloys and Compounds 333 (2002) 159 – 164
Fig. 3. Relaxation peaks in TiNi alloys.
annealed at 1163 K for 260 ks. The exothermic peak during cooling is due to the transformation from austenite to martensite, while the endothermic peak during heating is due to the transformation from martensite to austenite. The decrease in the internal friction and the Young’s modulus minimum corresponded to the DSC peaks in each sample. Therefore, the change in the internal friction and modulus seems to be dependent on the transformation from martensite to austenite. The large peaks, observed in the TN, N 1 and N 2 samples from 230 to 250 K did not correspond to the DSC peaks, and are not due to transformation. This peak might be due to thermally activated relaxation process, because it was observed at the same temperature during cooling and heating measurements.
161
Several types of relaxation peaks have been reported. Hasiguti and Igata [1] report a Bordoni type peak and point defect-dislocation interaction peaks in Ti and Ni. For TiNi, Hsiguti and Iwasaki [2] report a peak at 203 K with an activation energy of 0.38 eV and a frequency factor of 6310 9 s 21 . This might be due to a movement of dislocation or a movement of point-defect-pinned dislocations. Postnikow et al. [3] and Zhu et al. [4] also reported a peak of the same mechanism. Tirbonod and Koshimizu [5] reported a Bordoni type peak in an equiatomic TiNi alloy. The presence of this peak should be due to the motion of imperfect dislocations with a Burgers vector smaller than the lattice parameter. Coluzzi et al. [6] reported a frequency insensitive peak probably due to thermomechanical depinning of twin boundaries from point defects. Fig. 3 shows the Arrhenius plot for relaxation peaks of experimental results and present data. Curves A and B were also plotted from present data [2,5]. Experimental results agreed well with the curve A. Therefore, the observed relaxation peak might be due to a movement of dislocation or a movement of point-defect-pinned dislocations. Fig. 4 shows the diffraction patterns of the T 1 , T 2 , TN, N 1 and N 2 samples annealed at 1163 K for 260 ks (CuKa). A very broad TiNi line was observed in all these specimens. Patterns of Ti 2 Ni and TiNi 3 increased with the increase in the Ti and Ni contents, respectively. Fig. 5 is a TEM micrograph of the T 2 sample annealed at 1163 K for 260 ks. Many precipitates were observed at the interface of the martensite twins, although few precipitates were observed in the TN sample. From these facts, the effect of the Ti 2 Ni precipitation is considered as one of the reasons why the peak did not appear in the Ti-rich samples. In the temperature range .300 K, the Ti-rich samples showed a higher damping capacity. This is based on the fact that the transformation temperature is higher in Ti-rich samples. In the temperature range ,300 K, the TN sample shows a higher damping capacity due to the effect of the relaxation peak.
Fig. 4. Diffraction pattern of T 1 , T 2 , TN, N 1 and N 2 samples annealed at 1163 K for 260 ks. CuKa radiation; d, TiNi; ., Ti 2 Ni; m, TiNi 3 .
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K. Hishitani et al. / Journal of Alloys and Compounds 333 (2002) 159 – 164
Fig. 5. TEM micrograph of the T 2 sample annealed at 1163 K for 260 ks.
Fig. 7. DSC results of TN samples annealed at 1163 K for 21.6, 64.8 and 260 ks.
3.1.2. Effect of annealing time Fig. 6 shows the temperature dependence of the internal friction and Young’s modulus of the TN sample annealed at 1163 K for 21.6, 64.8 and 260 ks on the heating measurement. Decreases in the internal friction and Young’s modulus with austenite transformation were observed in all the samples. Fig. 7 shows the DSC curves of the TN sample annealed at 1163 K for 21.6, 64.8 and 260 ks. In the samples annealed for 21.6 and 64.8 ks, two peaks were observed in each of the cooling and heating runs. This shows that Ti- and Ni-rich areas exist in the material. In the sample annealed for 64.8 ks, a high damping capacity was observed in a wide temperature range. This might be due to the coexistence of the Ti- and
3.1.3. Effect of cooling rate Fig. 8 shows the temperature dependence of the internal friction and Young’s modulus of the WQ and RWQ specimens. The relaxation peak of the RWQ specimen was higher than that of the WQ specimen. Fig. 9 is TEM micrographs of the WQ and RWQ specimen. Compared with the WQ specimen, very fine martensite twins were
Fig. 6. Temperature dependency of the internal friction and Young’s modulus of TN samples annealed at 1163 K for 21.6 (d), 64.8 (m) and 260 ks (3) on heating measurement.
Fig. 8. Temperature dependency of the internal friction and Young’s modulus of WQ (3) and RWQ (d) specimens on heating measurements.
Ni-rich areas. When the TiNi alloy is produced by the lamination process, by controlling the ratio of the Ti- and Ni-rich areas by the annealing time, it is possible to obtain the damping effect by the transformation over a wide temperature range.
K. Hishitani et al. / Journal of Alloys and Compounds 333 (2002) 159 – 164
163
Fig. 11. Ultimate tensile strength of TN samples annealed at 1163 K for 21.6–864 ks.
3.2. Ultimate tensile strength
Fig. 9. TEM micrographs of TN samples at 1163 K for 260 ks; (a) WQ, (b) RWQ.
observed in the RWQ specimen. It is considered that this phenomenon is caused by the effect of the rapid cooling. The refinement of the martensite twins may be the reason of the heightened relaxation peak [7].
Fig. 10. Ultimate tensile strength of T 1 , T 2 , TN, N 1 and N 2 samples annealed at 1163 K for 260 ks.
Fig. 10 shows the ultimate tensile strength of the T 1 , T 2 , TN, N 1 and N 2 samples annealed at 1163 K for 260 ks. The ultimate tensile strength increased with the increase in the Ni content. Fig. 11 shows the ultimate tensile strength of the TN sample annealed at 1163 K for 21.6–864 ks. The tensile strength increased with the increase in the annealing time. These results show that the tensile strength can be controlled by the composition and the annealing time. Fig. 12 shows SEM micrographs of the TN sample annealed at 1163 K for 21.6 and 260 ks. Many voids were observed in each sample due to the Kirkendall effect. The Ti-rich layers were observed in the sample annealed for 21.6 ks. Based on the results of the XRD measurements and point analysis, this layer is estimated to be Ti 2 Ni in the Ti-rich samples annealed for 260 ks and the TN sample annealed for a shorter time, the Ti 2 Ni layers were also observed. From this fact, the effect of the Ti 2 Ni layer was considered as the origin of that these samples showed the lower tensile strength.
Fig. 12. SEM micrographs of TN samples annealed at 1163 K for 21.6 ks (a) 260 ks (b).
164
K. Hishitani et al. / Journal of Alloys and Compounds 333 (2002) 159 – 164
4. Summary In this paper, the processing of the TiNi alloy from the Ti–Ni laminated material by the solid-phase diffusion method and the effects of the composition, annealing time and cooling rate of the water quenching on the internal friction and tensile strength are reported. The main results are as follows 1. It was possible to produce the TiNi alloy from the Ti–Ni laminated material by the solid-phase diffusion method. 2. In the temperature range .300 K, the Ti-rich samples show a higher damping capacity. This value is higher in the Ti-rich samples due to the transformation temperature. In the temperature range ,300 K, the TN sample shows a higher damping capacity due to the effect of the relaxation peak, and this peak might be due to a movement of dislocations or a movement of pointdefect-pinned dislocations. 3. In the sample annealed for 64.8 ks, a high damping capacity was shown over a wide temperature range. It might be due to the coexistence of the Ti- and Ni-rich areas. When the TiNi alloy is produced by the lamination process, by controlling the ratio of the Ti- and Ni-rich areas by the annealing time, it is possible to obtain the damping effect by the transformation over the wide temperature range.
4. A material with an internal friction of d 50.14 at 250 K and ultimate tensile strength of about 800 MPa was obtained.
Acknowledgements The authors acknowledge the financial support of the Japan Society for the Promotion of Science Research and Development of New High Damping Material Based on Atomistic Design Project and the technical advice of Dr. K. Tsuchiya, Toyohashi University of Technology, who provided the DSC measurements.
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