Asymmetry of stress-strain curves under tension and compression for NiTi shape memory alloys

Journal Article · Fri Jul 24 04:00:00 EDT 1998 · Acta Materialia

DOI:https://doi.org/10.1016/S1359-6454(98)00112-8· OSTI ID:634671

Liu, Y; Xie, Z; Van Humbeeck, J; Delaey, L ^[1]

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1. Katholieke Univ. Leuven, Heverlee (Belgium)

The stress-strain curves of polycrystalline martensitic NiTi shape memory alloys are often different for loading under tension and compression. Under tension, a flat stress-plateau occurs, while under compression, the material is quickly strain hardened and no flat stress-plateau is observed. Cyclic deformation under tension-compression also shows that it is more difficult to deform the material during compression than during tension, where an asymmetric stress-strain loop is obtained. TEM observations show that, under tension to 4% strain, martensite variants are partially reoriented via migration of variant interfaces with formation of dislocation networks mainly along the junction plane areas, and no significantly plastic deformation has been observed inside the martensite twin bands. While under compression to 4% strain, a high density of dislocations has been generated in both the martensite twin bands and the variant accommodation area, and no significant martensite reorientation via variant interfacial migration has been observed. This shows that the deformation mechanism of martensitic polycrystalline NiTi SMAs under tension is different from that under compression.

• OSTI ID: 634671
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 12 Vol. 46; ISSN 1359-6454; ISSN ACMAFD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COMPRESSION STRENGTH
CORRELATIONS
DEFORMATION
DISLOCATIONS
MARTENSITE
MICROSTRUCTURE
NICKEL ALLOYS
SHAPE MEMORY EFFECT
TENSILE PROPERTIES
TITANIUM ALLOYS