Effects of deformation on microstructure and mechanical properties of a Cu-Al-Ni shape memory alloy

Journal Article · Tue Jul 15 00:00:00 EDT 2008 · Materials Characterization

DOI:https://doi.org/10.1016/j.matchar.2007.07.017· OSTI ID:21140745

Kirindi, T ^[1]

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1. Department of Computer Education and Instructional Technology, Faculty of Education, Kirikkale University, Yahsihan Campus, 71450 Kirikkale (Turkey)

In Cu-11.92 wt.%Al-3.78 wt.%Ni shape memory alloy, the influence of deformation and thermal treatments on the microstructure and mechanical properties under the compression test were studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). Experiments show that the mechanical properties of the alloy can be enhanced by convenient heat treatments. The alloy exhibits good mechanical properties with high ultimate compression strength and ductility after annealing at high temperature. However, it exhibits brittle fracture and dramatic strain hardening, with linear stress-strain behavior after annealing at low temperature. The changes in the mechanical properties have been linked to the evolution of the degree of order, occurrence of precipitation, and variation of the grain size. From microstructural observations, it is seen that the {beta}{sub 1}' (18R) and {gamma}{sub 1}' (2H) martensite phases coexist at different fractions in the undeformed and deformed states. Deformation induces the changes between the {beta}{sub 1}' and {gamma}{sub 1}' martensites and deformation-induced martensites form at preferred orientations as mechanical twins. The {beta}{sub 1}' martensite variants are twin-related with respect to the (1-bar 2-bar 8){sub 18R} mirror plane and a new orientation relationship for these twin variants is derived as (1-bar 2-bar 8){sub A}-parallel (1-bar 2-bar 8){sub C}: [4-bar 61] {sub A}-parallel [4-bar 61]{sub C}. Additionally, an increase in the amount of deformation causes martensite reorientation, de-twinning, and dislocation generation; also, the martensite plates are seen to have rearranged in the same orientation to be parallel with each other.

• OSTI ID: 21140745
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Journal Issue: 7 Vol. 59; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
ANNEALING
CALORIMETRY
COMPRESSION STRENGTH
COPPER ALLOYS
DEFORMATION
DISLOCATIONS
DUCTILITY
FRACTURES
GRAIN ORIENTATION
GRAIN SIZE
MARTENSITE
METALLURGICAL EFFECTS
NICKEL ALLOYS
PHASE TRANSFORMATIONS
PLASTICITY
PRECIPITATION
SCANNING ELECTRON MICROSCOPY
STRAIN HARDENING
STRAINS
STRESSES
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0400-1000 K
TRANSMISSION ELECTRON MICROSCOPY
TWINNING