TY - JOUR

T1 - Shape memory and pseudoelastic behavior of 51.5%Ni-Ti single crystals in solutionized and overaged state

AU - Sehitoglu, H.

AU - Jun, J.

AU - Zhang, Y.-X.

AU - Karaman, I.

AU - Chumlyakov, Y.

AU - Maier, H. J.

AU - Gall, K.

N1 - Funding Information: Portions of the research is supported by a grant from the National Science Foundation contract CMS 99-00090, Mechanics and Materials Program, Arlington, Virginia, and Air Force Office of Scientific Research, Directorate of Aerospace and Materials Sciences, Arlington, Virginia. Professor Chumlyakov received support from the Russian Fund for Basic Researches, Grant Nos. 02-95-00350, 99-03-32579. The facilities at Microanalysis of Materials, Materials Research Laboratory were used. This laboratory is funded by DOE-DMS grant DEFGO2-96ER45439.

PY - 2001/10/9

Y1 - 2001/10/9

N2 - Deformation of nickel rich (51.5%Ni) Ni-Ti single crystals are investigated over a wide range of temperatures (77-440 K) and strain levels in compression as high as 9%. These alloys combine high strength with an unusually wide pseudoelasticity temperature interval (near 200 K) and can be exploited to suit specific applications. The slip deformation in [001] orientation can not occur due to the prevailing slip systems, as confirmed by transmission electron microscopy. Consequently, the [001] orientation exhibited pseudoleastic deformation at temperatures ranging from 77 to 283 K for the solutionized case and 273-440 K for the aged condition respectively. The critical transformation stress levels were in the range 800-1800 MPa for the solutionized case, and 200-1000 MPa for the aged case depending on the temperature and specimen orientation. These stress levels are considerably higher compared to the near equiatomic Ni compositions of these class of alloys. On the other hand, the maximum transformation str ains, measured from incremental straining experiments in compression, were lower compared to both the phenomenological theory with Type II twinning and the previous experimental work on 50.8%Ni NiTi crystals. A new theory for compound twinning is introduced with lattice invariant shear as a solution, and relies on the successive austenite phase (B2) to intermediate phase (R) to martensite phase (B 19′) transformation. The compound twinning model predicts lower transformation strains compared to the Type II twinning case lending an explanation of the experimental transformation strain levels.

AB - Deformation of nickel rich (51.5%Ni) Ni-Ti single crystals are investigated over a wide range of temperatures (77-440 K) and strain levels in compression as high as 9%. These alloys combine high strength with an unusually wide pseudoelasticity temperature interval (near 200 K) and can be exploited to suit specific applications. The slip deformation in [001] orientation can not occur due to the prevailing slip systems, as confirmed by transmission electron microscopy. Consequently, the [001] orientation exhibited pseudoleastic deformation at temperatures ranging from 77 to 283 K for the solutionized case and 273-440 K for the aged condition respectively. The critical transformation stress levels were in the range 800-1800 MPa for the solutionized case, and 200-1000 MPa for the aged case depending on the temperature and specimen orientation. These stress levels are considerably higher compared to the near equiatomic Ni compositions of these class of alloys. On the other hand, the maximum transformation str ains, measured from incremental straining experiments in compression, were lower compared to both the phenomenological theory with Type II twinning and the previous experimental work on 50.8%Ni NiTi crystals. A new theory for compound twinning is introduced with lattice invariant shear as a solution, and relies on the successive austenite phase (B2) to intermediate phase (R) to martensite phase (B 19′) transformation. The compound twinning model predicts lower transformation strains compared to the Type II twinning case lending an explanation of the experimental transformation strain levels.

KW - Martensite

KW - Phase transformations

KW - Shape memory

KW - Single crystal

KW - Transmission Electron Microscopy (TEM)

UR - http://www.scopus.com/inward/record.url?scp=0035834198&partnerID=8YFLogxK

U2 - 10.1016/S1359-6454(01)00216-6

DO - 10.1016/S1359-6454(01)00216-6

M3 - Article

AN - SCOPUS:0035834198

VL - 49

SP - 3609

EP - 3620

JO - Acta materialia

JF - Acta materialia

SN - 1359-6454

IS - 17

ER -