Microstructures and phase transformations of Ti-30Zr-xNb (x = 5, 7, 9, 13 at.%) shape memory alloys

Journal Article · Thu Dec 15 00:00:00 EST 2016 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2016.10.019· OSTI ID:22689660

Qu, Wentao; Sun, Xuguang; Yuan, Bifei ^[1]; Xiong, Chengyang; Zhang, Fei ^[2]; Li, Yan ^[2]; Sun, Baohui ^[3]

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1. School of Mechanical Engineering, Xi'an Shiyou University, Xi'an 710065 (China)
2. School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)
3. Lanzhou Seemine SMA Co. Ltd., Lanzhou 730010 (China)

The microstructures, phase transformations and shape memory properties of Ti-30Zr-xNb (x = 5, 7, 9, 13 at.%) alloys were investigated. The X-ray diffraction and transmission electron microscopy observations showed that the Ti-30Zr-5Nb, Ti-30Zr-7/9Nb and Ti-30Zr-13Nb alloys were composed of the hcp α′-martensite, orthorhombic α″-martensite and β phases, respectively. The results indicated the enhanced β-stabilizing effect of Nb in Ti-30Zr-xNb alloys than that in Ti-Nb alloys due to the high content of Zr. The differential scanning calorimetry test indicated that the Ti-30Zr-5Nb alloy displayed a reversible transformation with a high martensitic transformation start temperature of 776 K and a reverse martensitic transformation start temperature (A{sub s}) of 790 K. For the Ti-30Zr-7Nb and Ti-30Zr-9Nb alloys, the martensitic transformation temperatures decreased with the increasing Nb content. Moreover, an ω phase transformation occurred in the both alloys upon heating at a temperature lower than the corresponding A{sub s}, which is prompted by more addition of Nb. Although the critical stress in tension of the three martensitic alloys decreased with increasing Nb content, the Ti-30Zr-9Nb alloy showed a critical stress of as high as 300 MPa. Among all the alloys, the Ti-30Zr-9Nb alloy exhibited the maximum shape memory effect of 1.61%, due to the lowest critical stress for the martensite reorientation. - Highlights: •Ti-30Zr-5Nb alloy is composed of hcp α′-martensite with the M{sub s} of 776 K. •Ti-30Zr-7Nb and Ti-30Zr-9Nb alloys are predominated by orthorhombic α″-martensite. •Ti-30Zr-13Nb alloy consists of a single β phase due to the β-stabilizing effect of Nb. •The martensitic transformation temperatures decrease with increasing Nb content. •Ti-30Zr-9Nb alloy shows the maximum shape memory effect of 1.61%.

• OSTI ID: 22689660
• Journal Information: Materials Characterization, Vol. 122; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-5803
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CALORIMETRY
HCP LATTICES
HEATING
IRON-ALPHA
MARTENSITE
MARTENSITIC STEELS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NIOBIUM ALLOYS
ORTHORHOMBIC LATTICES
PHASE TRANSFORMATIONS
SHAPE MEMORY EFFECT
STRESSES
TEMPERATURE RANGE 0400-1000 K
TITANIUM ALLOYS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION