Effect of grain size on stress induced martensitic transformations in a Cu-Al-Be polycrystalline shape-memory alloy. Pseudoelastic cycling effects and microstructural modifications

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:609

Article

Sade, M.^1,2,3  de Castro Bubani, F.^1,2  Lovey, F. C.^1,3  Torra, V.⁴ 

[1] Ctr Atom Bariloche CNEA, RA-8400 San Carlos De Bariloche, Rio Negro, Argentina

[2] Consejo Nacl Invest Cient & Tecn, RA-1033 Buenos Aires, DF, Argentina

[3] Univ Nacl Cuyo, Inst Balseiro, RA-8400 San Carlos De Bariloche, Rio Negro, Argentina

[4] Univ Politecn Cataluna, Barcelona 08034, Spain

关键词: Martensitic transformations;    Shape-memory effect;    Pseudoelasticity;    Transmission electron microscopy;    Mechanical properties;    Cu-base alloys;   

DOI  :  10.1016/j.msea.2014.05.018

来源: Elsevier

【 摘 要 】

Grain size has a strong effect on the pseudoelastic properties of shape-memory alloys. Different grain sizes and several related phenomena are studied. This involves the dependence of the transformation and retransformation stresses on grain size and on the amount of transformed material. A pronounced drop of transformation stresses on cycling is observed, until an asymptotic behavior is reached. This is related to the creation of defects (dislocations and dislocation arrays) and microplates of martensite, which are the defects necessary to allow the grains to accommodate due to the shape change imposed by the martensitic transformation. The asymptotic hysteresis is related to the internal work for the grains to accommodate each other once the necessary defects were created. The asymptotic hysteresis increases linearly as the grain size decreases. A simple model shows that the slope is related to the (d/e) ratio, where d is the average grain size and e is the width of the specimen. This effect arises from the presence of the free surfaces that release the plastic work for grain accommodation. (C) 2014 Elsevier B.V. All rights reserved.

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