Origin of the two-way memory effect in NiTi shape memory alloys

Journal Article · Tue Jun 01 00:00:00 EDT 1993 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(93)90492-B· OSTI ID:6401893

Manach, P Y; Favier, D ^[1]

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1. Inst. National Polytechnique de Grenoble, Saint Martin d'Heres (France)

It is now well-known that the two-way memory effect (TWME) of shape memory alloys is obtained after a thermomechanical cycling called training. Although this point is well-admitted, many controversies still subsist on the physical origin of this two-memory effect. The explanations of the development of the TWME which are often given are either the presence after training of a low proportion of local stabilized martensite in the parent phase or the presence after training of an internal stress field in the material. Recently, in a systematic study of the two-way memory effect obtained by thermomechanical training cycles under homogeneous tensile constant load, Stalmans et. al. disproved these two previous explanations. Following the study, the most important effect of the dislocation arrays which are introduced during the training is not to develop internal stresses but rather to give rise to a microstructural anisotropy inducing a thermodynamic anisotropy. It means that after training, the crystallographically equivalent martensite variants are no more thermodynamically equivalent. The present paper describes some experimental results obtained by the homogeneous simple shear training of a NiTi shape memory alloy. The experiments have been specifically designed to give new comprehension elements on the existence and the nature of the thermodynamic anisotropy developed during training.

• OSTI ID: 6401893
• Journal Information: Scripta Metallurgica et Materialia; (United States), Vol. 28:11; ISSN 0956-716X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
NICKEL ALLOYS
SHAPE MEMORY EFFECT
TITANIUM ALLOYS
ANISOTROPY
DISLOCATIONS
EXPERIMENTAL DATA
INTERMETALLIC COMPOUNDS
MECHANICAL TESTS
MICROSTRUCTURE
ORIGIN
STRAIN RATE
THERMOMECHANICAL TREATMENTS
ALLOYS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DATA
FABRICATION
HEAT TREATMENTS
INFORMATION
LINE DEFECTS
MATERIALS TESTING
MATERIALS WORKING
NUMERICAL DATA
TESTING
360102* - Metals & Alloys- Structure & Phase Studies
360103 - Metals & Alloys- Mechanical Properties