TY - JOUR

T1 - Strain-temperature behavior of NiTiCu shape memory single crystals

AU - Sehitoglu, H.

AU - Karaman, I.

AU - Zhang, Y.-X.

AU - Viswanath, A.

AU - Chumlyakov, Y.

AU - Maier, H. J.

N1 - Funding Information: The research is supported by a grant from the Department of Energy, Basic Energy Sciences Division, Germantown, Maryland, DOE DEFG02-93ER14393 and the National Science Foundation contract CMS 99-00090, Mechanics and Materials Program, Arlington, Virginia. Professor Chumlyakov received support from the Russian Fund for Basic Researches, Grants No. 02-95-00350 and 03-99-32579. The facilities at Microanalysis of Materials, Materials Research Laboratory were used. This laboratory is funded by DOE-DMS grant DEFG02-96ER45439.

PY - 2001/10/9

Y1 - 2001/10/9

N2 - Single crystal specimens of NiTi10Cu alloys were subjected to temperature cycling conditions under constant tensile and compressive stresses and the transformation strains were monitored. The [111] orientation exhibited the highest experimental transformation strains (6.64%) in tension while the [001] provides the highest transformation strains in compression (5.34%). These transformation strain levels are significantly higher than previously reported values on NiTiCu alloys. The theoretical treatment includes both the calculation of the CVP (correspondent variant pair) formation strain incorporating the growth of monoclinic phase from the most favorably oriented orthorhombic variant, and the concomitant detwinning of the monoclinic martensite. The experimental transformation strain values are consistently below the theoretical levels due to two main reasons: the slip deformation in the austenite domains as confirmed with TEM studies, and the incomplete transformation resulting in a mixture of orthorhomb ic and monoclinic phases as determined from diffraction patterns. The experimental transformation strains are higher in tension compared to compression for most single crystal orientations due to two factors: the additional strain associated with the detwinning of the B19′phase in the final microstructure (such as in [111] case), and the partial completion of the second step of the transformation limiting the compression strains.

AB - Single crystal specimens of NiTi10Cu alloys were subjected to temperature cycling conditions under constant tensile and compressive stresses and the transformation strains were monitored. The [111] orientation exhibited the highest experimental transformation strains (6.64%) in tension while the [001] provides the highest transformation strains in compression (5.34%). These transformation strain levels are significantly higher than previously reported values on NiTiCu alloys. The theoretical treatment includes both the calculation of the CVP (correspondent variant pair) formation strain incorporating the growth of monoclinic phase from the most favorably oriented orthorhombic variant, and the concomitant detwinning of the monoclinic martensite. The experimental transformation strain values are consistently below the theoretical levels due to two main reasons: the slip deformation in the austenite domains as confirmed with TEM studies, and the incomplete transformation resulting in a mixture of orthorhomb ic and monoclinic phases as determined from diffraction patterns. The experimental transformation strains are higher in tension compared to compression for most single crystal orientations due to two factors: the additional strain associated with the detwinning of the B19′phase in the final microstructure (such as in [111] case), and the partial completion of the second step of the transformation limiting the compression strains.

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=0035834211&partnerID=8YFLogxK

U2 - 10.1016/S1359-6454(01)00192-6

DO - 10.1016/S1359-6454(01)00192-6

M3 - Article

AN - SCOPUS:0035834211

VL - 49

SP - 3621

EP - 3634

JO - Acta materialia

JF - Acta materialia

SN - 1359-6454

IS - 17

ER -