TY - JOUR

T1 - Cyclic degradation mechanisms in aged FeNiCoAlTa shape memory single crystals

AU - Krooß, P.

AU - Somsen, C.

AU - Niendorf, T.

AU - Schaper, M.

AU - Karaman, I.

AU - Chumlyakov, Y.

AU - Eggeler, G.

AU - Maier, H. J.

N1 - Funding information: Financial support by Deutsche Forschungsgemeinschaft under Grant No. MA 1175/33-1 is gratefully acknowledged. The reported study was partially supported by RFBR Project No. 12-08-91331 NNIO-a. I.K. acknowledges the financial support by the US National Science Foundation—International Materials Institute Program through the grant no. DMR 08-44082, Division of Materials Research, Arlington, Virginia. C.S. and G.E. acknowledge funding by the Deutsche Forschungsgemeinschaft (DFG) in the framework of FOR 1766, Project TP2.

PY - 2014/10/15

Y1 - 2014/10/15

N2 - This study focuses on the functional stability of [0 0 1]-oriented Fe 41Ni28Co17Al11.5Ta2.5 (at.%) single crystals. It is shown that functional degradation of aged FeNiCoAlTa, containing fine dispersed γ′-particles ∼5-8 nm in diameter is caused by the interaction of different martensite variants under cyclic loading in tension. Superelastic cycling experiments up to 4.5% total strain resulted in the accumulation of permanent strain mainly caused by the formation of retained martensite. In situ observations were conducted in order to evaluate the local strain evolution and martensite variant interactions on the meso- and microscale. Optical microscopy and transmission electron microscopy observations revealed various differently oriented martensite variants which were retained upon 100 superelastic cycles. In addition, fine martensitic structures remaining in the vicinity of the γ′ precipitates were found after mechanical cycling, which are shown to be important for cyclic degradation in Fe-based shape memory alloys.

AB - This study focuses on the functional stability of [0 0 1]-oriented Fe 41Ni28Co17Al11.5Ta2.5 (at.%) single crystals. It is shown that functional degradation of aged FeNiCoAlTa, containing fine dispersed γ′-particles ∼5-8 nm in diameter is caused by the interaction of different martensite variants under cyclic loading in tension. Superelastic cycling experiments up to 4.5% total strain resulted in the accumulation of permanent strain mainly caused by the formation of retained martensite. In situ observations were conducted in order to evaluate the local strain evolution and martensite variant interactions on the meso- and microscale. Optical microscopy and transmission electron microscopy observations revealed various differently oriented martensite variants which were retained upon 100 superelastic cycles. In addition, fine martensitic structures remaining in the vicinity of the γ′ precipitates were found after mechanical cycling, which are shown to be important for cyclic degradation in Fe-based shape memory alloys.

KW - Fatigue

KW - Internal friction

KW - Martensitic phase transformation

KW - Precipitates

KW - Shape memory alloys

UR - http://www.scopus.com/inward/record.url?scp=84905864817&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2014.06.019

DO - 10.1016/j.actamat.2014.06.019

M3 - Article

AN - SCOPUS:84905864817

VL - 79

SP - 126

EP - 137

JO - Acta materialia

JF - Acta materialia

SN - 1359-6454

ER -