Texture Development in the Ni47Ti44Nb9 Shape Memory Alloy During Successive Thermomechanical Processing and Its Effect on Shape Memory and Mechanical Properties

Yan, Ying; Jin, Wei; Li, X. W.

doi:10.1007/s11661-012-1426-8

Cited by 6 publications

(8 citation statements)

References 26 publications

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“…The grain sizes for the cast and sheet material were determined as 300 µm and 300 nm, respectively, using the Intercept Procedure from ASTM E112-12. Texture is rarely reported (Yan et al, 2012) and it is likewise beyond the scope of this work. The impact of differential thermo-mechanical processing was contrast by studying an extruded rod material (3.45 mm diameter) provided by Memry Corporation with the composition of Ni 44.6 Ti 42.8 Nb 12.6 (at%).…”

Section: Materials Characterizationmentioning

confidence: 94%

“…The SEM image in Figure 3(b) shows the typical eutectic micro-constituent, which is made up of β-Nb-rich particles and α-NiTiNb matrix (Siegert et al, 2002; Wang et al, 2014; Zhao, 2000). Deformation processing breaks up the net-like structure (Siegert et al, 2002; Wang et al, 2014; Yan et al, 2012). The micro-constituent morphology for the sheet material is shown in Figure 3(c).…”

Section: Materials Characterizationmentioning

confidence: 99%

“…It is well known that the unique stabilization of martensite, which is the cornerstone of NiTiNb shape memory behavior, is attributed to the micro-constituent morphologies (Cai et al, 1994; Kusagawa et al, 2001; Melton et al, 1988; Siegert et al, 2002; Wang et al, 2014; Yan et al, 2012; Zhao, 2000). The microstructure images in Figure 3(c) and (d) underscore differential micro-constituent morphologies resulting from different thermo-mechanical processing done by the different companies, which show the sheet and rod materials, respectively.…”

Section: Materials Characterizationmentioning

confidence: 99%

“…First, the process of self-post-tensioning with SMA tendons and the required conditions on the transformation temperatures of the SMAs are discussed. The alloys are typically cast and further cold- or hot-worked into rods, sheets, tubes, wires, and so on for practical application (Siegert et al, 2002; Wang et al, 2014; Yan et al, 2012). Thus, in this work, commercially available rod and sheet NiTiNb materials are contrast with respect to a cast NiTiNb alloy in order to benchmark the influence of differential deformation processes.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Feasibility of self-pre-stressing concrete members using shape memory alloys

Ozbulut

Hamilton

Sherif

et al. 2015

Journal of Intelligent Material Systems and Structures

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Shape memory alloys are a class of smart materials that recover apparent plastic deformation (∼6%–8% strain) after heating, thus “remembering” the original shape. This shape memory effect can be exploited for self-post-tensioning applications, and NiTi-based shape memory alloys are promising as shape memory effect is possible at elevated temperatures amenable to practical application compared to conventional NiTi. This study investigates the feasibility of self-post-tensioned concrete elements by activating the shape memory effect of NiTiNb, a class of wide-hysteresis shape memory alloys, using the heat of hydration of grout. First, the microstructure characterization of the NiTiNb wide-hysteresis shape memory alloys is discussed. Then, the tensile stress-induced martensitic transformations in NiTiNb shape memory alloy tendons are studied. Next, the temperature increase due to the heat of hydration of four commercially available grouts is investigated. Pull-out tests are also conducted to investigate the bond between the grout and shape memory alloy bar. Results show that the increase in temperature due to hydration heat can provide significant strain recovery during a free recovery experiment, while the same temperature increase only partially activates the shape memory alloys during a constrained recovery.

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Section: Materials Characterizationmentioning

confidence: 94%

Section: Materials Characterizationmentioning

confidence: 99%

Section: Materials Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Feasibility of self-pre-stressing concrete members using shape memory alloys

Ozbulut

Hamilton

Sherif

et al. 2015

Journal of Intelligent Material Systems and Structures

View full text Add to dashboard Cite

show abstract

“…Several investigations characterize the impact of deformation processing conditions on the microstructure [19,25,[31][32][33][34][35]. Ultimately, the findings show that the deformationprocessed microstructure is made up of oriented b-Nb-rich microconstituents that are dispersed throughout the matrix similar to aligned discontinuous fiber (or nanowire)-reinforced composites [36][37][38].…”

Section: Introductionmentioning

confidence: 99%

Shape Memory Effect in Cast Versus Deformation-Processed NiTiNb Alloys

Hamilton

Lanba

Ozbulut

et al. 2015

Shap. Mem. Superelasticity

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The shape memory effect (SME) response of a deformation-processed NiTiNb shape memory alloy is benchmarked against the response of a cast alloy. The insoluble Nb element ternary addition is known to widen the hysteresis with respect to the binary NiTi alloy. Cast microstructures naturally consist of a cellular arrangement of characteristic eutectic microconstituents surrounding primary matrix regions. Deformation processing typically aligns the microconstituents such that the microstructure resembles discontinuous fiber-reinforced composites. Processed alloys are typically characterized for heat-to-recover applications and thus deformed at constant temperature and subsequently heated for SME recovery, and the critical stress levels are expected to facilitate plastic deformation of the microconstituents. The current work employs thermal cycling under constant bias stresses below those critical levels. This comparative study of cast versus deformation-processed NiTiNb alloys contrasts the straintemperature responses in terms of forward DT F = M s-M f and reverse DT R = A f-A s temperature intervals, the thermal hysteresis, and the recovery ratio. The results underscore that the deformation-processed microstructure inherently promotes irreversibility and differential forward and reverse transformation pathways.

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