Microstructure of NiTi shape memory alloy due to tension-compression cyclic deformation

Journal Article · Mon Mar 23 04:00:00 EST 1998 · Acta Materialia

DOI:https://doi.org/10.1016/S1359-6454(97)00379-0· OSTI ID:616249

Xie, Z; Liu, Y; Humbeeck, J van ^[1]

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1. Catholic Univ. of Leuven, Heverlee (Belgium). Dept. of Metallurgy and Materials Engineering

Experimental results have shown that, during mechanical cycling under tension-compression load within {+-}4% strains, the NiTi shape memory alloy is cyclic strain-hardened. The maximum stresses under both tension and compression increase with increasing number of cycles and tend to stabilize with further cycling. The present work is focused on the martensite microstructure developed as a result of mechanical cycling. TEM observations show that, before cycling, the martensite variants are well self-accommodated to each other with the <011> type II twinning as the main lattice invariant shear. After mechanical cycling, the martensite plates are still self-accommodated and the (11{bar 1}) type I twinning is most frequently observed. In addition to the stress-induced re-orientation of martensite and twin boundary movement within the martensite plate, various lattice defects have been developed both in the junction plane areas of martensite plates and within the martensite twins.

• OSTI ID: 616249
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 6 Vol. 46; ISSN 1359-6454; ISSN ACMAFD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
DEFORMATION
MICROSTRUCTURE
NICKEL ALLOYS
SHAPE MEMORY EFFECT
STRAIN HARDENING
TITANIUM ALLOYS