Transformation behaviors and shape memory characteristics of Ti-50.2Ni (at.%) alloy which had been cold-worked after solution -treatment were investigated. The B2-R–B19’transformation occurred on cooling in the cold-worked samples, while the B2-B19’ transformation occurred in the solution-tre...
Transformation behaviors and shape memory characteristics of Ti-50.2Ni (at.%) alloy which had been cold-worked after solution -treatment were investigated. The B2-R–B19’transformation occurred on cooling in the cold-worked samples, while the B2-B19’ transformation occurred in the solution-treated sample. M* (the DSC peak temperature corresponding to the R–B19’ transformation) decreased with increase of the amount of cold -working, while R* (the DSC peak temperature corresponding to the B2-R transformation) kept almost constant. The transformation elongation occurred under the applied stress of 10 MPa in the solution-treated sample was negligible, while that in the cold -worked sample (9%) was 3%. The residual elongation increased with increase of the amount of cold-working under the applied stress smaller than about 70 MPa, while that decreased under the applied stress larger than about 70 MPa.
The warm worked Ti-50.0Ni (at.%) were investigated by means of DSC, XRD and tensile test. Ti-50.0Ni (at.%) alloys which solution heat treatment occurred B2-B19’transformation. While the warm worked treatment occurred B2-R-B19’and R phase was observed all sample. Aging and thermo-mechanically treated Ti-50.2Ni (at.%) alloys were investigated by means of differential scanning calorimetry, X-ray diffractions and tensile tests. M* temperatures of 6% cold-worked specimens were almost constant when the annealing temperature increased to 673 K. M* temperatures of both 6% and 28% cold-worked specimens decreased rapidly with increase of annealing temperature from 673 K to 723 K. M* temperature increased drastically when specimen was annealed at temperatures higher than 773 K. R* temperature increased with increase of annealing temperature until annealing temperature increased to 673 K. R* temperature decreased when the annealing temperature was higher than 723 K. The plateau stage of stress-induced martensitic transformation was not observed for specimen that was 39% cold-worked and annealed at 573 K, but for specimens annealed at 673 K and 773 K, the plateau stage was observed definitely. The critical stress for inducing martensitic transformation increased from 260 MPa to 360 MPa with the ratio of cold working increased from 17% to 39%.
Transformation behaviors, shape memory characteristics and super elasticity of thermo-mechanically treated Ti-(45.0-x)Ni–5.0Cu-xV (x=0.5∼2.0 at.%) alloys were investigated by means of differential scanning calorimetry, transmission electron microscopy, X-ray diffractions, thermal cycling tests under constant load, tensile tests and electrical resistivity measurements. The B2-B19’ transformation occurs when V content was more than 0.5 (at.%), above which the B2-B19-B19’transformation occurred. The B2-B19’transformations was not separated clearly from the B19-B19’transformation. thermo-mechanically treated Ti-(45.0-x)Ni–5.0Cu-xV (at.%) alloys showed perfect shape memory effect and transformation hysteresis(ΔT) of Ti-43.5Ni-5.0Cu-1.5V and Ti–43.0Ni-5.0Cu-2.0V alloys were about 9 K which was much smaller than that of a Ti-44.5Ni -5.0Cu-0.5V alloy (23.3 K). More than 90% of superelastic recovery ratio was observed in all specimens and transformation hysteresis (Δσ) of a Ti-44.5Ni–5.0Cu-0.5V alloy was about 70 MPa, which was much lager than that of a Ti-43.0Ni-5.0Cu-2.0V alloy (35 MPa).
Ti-Ni-X (Ag, In, Sn, Sb, Te, Tl, Pb, Bi) ternary alloys were investigated. All specimens consisted of Ti-Ni matrices and second phase particles. Ag, In and Sn were soluble in Ti-Ni matrices with a limited solubility (≤1.0 at.%), while Sb, Te, Tl, Pb and Bi were not soluble. Two-stage B2-R-B19’transformation occurred in Ti-48.8Ni -1.2Ag, Ti-49.0Ni-1.0In and Ti-49.0Ni-1.0Sn alloys, while one-stage B2—B19’transformation occurred in Ti-49.0Ni-1.0Ag, Ti-49.0Ni- 1.0Sb, Ti-49.0Ni-1.0Te, Ti-49.0Ni-1.0Pb and Ti-49.0Ni-1.0Bi alloys. Micro Vickers hardness of the alloys displaying the B2-R-B19’transformation (Hv 250∼368) was much larger than that (≤Hv 200) of the alloys displaying the B2—B19’transformation. Solid solution hardening was an important factor for inducing the B2-R transformation in Ti-Ni-X (X=non–transition elements) alloys.
Transformation behaviors and shape memory characteristics of Ti-50.2Ni (at.%) alloy which had been cold-worked after solution -treatment were investigated. The B2-R–B19’transformation occurred on cooling in the cold-worked samples, while the B2-B19’ transformation occurred in the solution-treated sample. M* (the DSC peak temperature corresponding to the R–B19’ transformation) decreased with increase of the amount of cold -working, while R* (the DSC peak temperature corresponding to the B2-R transformation) kept almost constant. The transformation elongation occurred under the applied stress of 10 MPa in the solution-treated sample was negligible, while that in the cold -worked sample (9%) was 3%. The residual elongation increased with increase of the amount of cold-working under the applied stress smaller than about 70 MPa, while that decreased under the applied stress larger than about 70 MPa.
The warm worked Ti-50.0Ni (at.%) were investigated by means of DSC, XRD and tensile test. Ti-50.0Ni (at.%) alloys which solution heat treatment occurred B2-B19’transformation. While the warm worked treatment occurred B2-R-B19’and R phase was observed all sample. Aging and thermo-mechanically treated Ti-50.2Ni (at.%) alloys were investigated by means of differential scanning calorimetry, X-ray diffractions and tensile tests. M* temperatures of 6% cold-worked specimens were almost constant when the annealing temperature increased to 673 K. M* temperatures of both 6% and 28% cold-worked specimens decreased rapidly with increase of annealing temperature from 673 K to 723 K. M* temperature increased drastically when specimen was annealed at temperatures higher than 773 K. R* temperature increased with increase of annealing temperature until annealing temperature increased to 673 K. R* temperature decreased when the annealing temperature was higher than 723 K. The plateau stage of stress-induced martensitic transformation was not observed for specimen that was 39% cold-worked and annealed at 573 K, but for specimens annealed at 673 K and 773 K, the plateau stage was observed definitely. The critical stress for inducing martensitic transformation increased from 260 MPa to 360 MPa with the ratio of cold working increased from 17% to 39%.
Transformation behaviors, shape memory characteristics and super elasticity of thermo-mechanically treated Ti-(45.0-x)Ni–5.0Cu-xV (x=0.5∼2.0 at.%) alloys were investigated by means of differential scanning calorimetry, transmission electron microscopy, X-ray diffractions, thermal cycling tests under constant load, tensile tests and electrical resistivity measurements. The B2-B19’ transformation occurs when V content was more than 0.5 (at.%), above which the B2-B19-B19’transformation occurred. The B2-B19’transformations was not separated clearly from the B19-B19’transformation. thermo-mechanically treated Ti-(45.0-x)Ni–5.0Cu-xV (at.%) alloys showed perfect shape memory effect and transformation hysteresis(ΔT) of Ti-43.5Ni-5.0Cu-1.5V and Ti–43.0Ni-5.0Cu-2.0V alloys were about 9 K which was much smaller than that of a Ti-44.5Ni -5.0Cu-0.5V alloy (23.3 K). More than 90% of superelastic recovery ratio was observed in all specimens and transformation hysteresis (Δσ) of a Ti-44.5Ni–5.0Cu-0.5V alloy was about 70 MPa, which was much lager than that of a Ti-43.0Ni-5.0Cu-2.0V alloy (35 MPa).
Ti-Ni-X (Ag, In, Sn, Sb, Te, Tl, Pb, Bi) ternary alloys were investigated. All specimens consisted of Ti-Ni matrices and second phase particles. Ag, In and Sn were soluble in Ti-Ni matrices with a limited solubility (≤1.0 at.%), while Sb, Te, Tl, Pb and Bi were not soluble. Two-stage B2-R-B19’transformation occurred in Ti-48.8Ni -1.2Ag, Ti-49.0Ni-1.0In and Ti-49.0Ni-1.0Sn alloys, while one-stage B2—B19’transformation occurred in Ti-49.0Ni-1.0Ag, Ti-49.0Ni- 1.0Sb, Ti-49.0Ni-1.0Te, Ti-49.0Ni-1.0Pb and Ti-49.0Ni-1.0Bi alloys. Micro Vickers hardness of the alloys displaying the B2-R-B19’transformation (Hv 250∼368) was much larger than that (≤Hv 200) of the alloys displaying the B2—B19’transformation. Solid solution hardening was an important factor for inducing the B2-R transformation in Ti-Ni-X (X=non–transition elements) alloys.
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