Influence of Thermomechanical Treatment on Structural-Phase Transformations and Mechanical Properties of the Cu–Al–Ni Shape-Memory Alloys

Journal Article · Tue Jan 15 00:00:00 EST 2019 · Russian Physics Journal

DOI:https://doi.org/10.1007/S11182-018-1587-Z· OSTI ID:22943385

Svirid, A. E., E-mail: [e-mail]; Kuranova, N. N., E-mail: [e-mail]; Lukyanov, A. V., E-mail: [e-mail]; Makarov, V. V., E-mail: [e-mail]; Nikolayeva, N. V., E-mail: [e-mail]; Pushin, V. G., E-mail: [e-mail]; Uksusnikov, A. N., E-mail: [e-mail] ^[1]

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1. M. N. Mikheev Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences (Russian Federation)

Using the methods of optical and electron microscopy and electron and X-ray diffraction analyses, the influence of thermomechanical treatment on the mechanical properties, average grain size, and structural and phase transformations is investigated in the Cu–Al–Ni triple alloys exhibiting a shape memory effect. In the alloys under study with a fixed content of 3wt% Ni the concentration of aluminum was varied from 9 to 14 wt%. It is shown that in the alloys subjected to thermal treatment, including forging and homogenizing annealing using controlled recrystallization in the austenitic state followed by quenching, the grain-boundary disintegration and segregation disappear. It is found out that the microstructure of the alloys in the hot-forged and hardened states with the content of aluminum 9–10 wt%. consists of the grains of the average dimensions within 60–80 μm, with the content of aluminum 10–12 wt% – 100–350 μm, while in the alloys with the content of aluminum up to 14 12 wt% the average grain size reaches 1 mm. According to the data of mechanical testing at room temperature, with a decrease in the content of aluminum the ultimate tensile strength (σ{sub UTS}), the yield strength (σ{sub М}) and the relative elongation (δ) increase. An improvement of the mechanical properties of the alloys is attributed to the grain structure refinement of the β{sub 2}-austenite and package substructure of the β'{sub 1}-and γ'{sub 1}-martensites as the content of aluminum in the alloys decreases. For instance, in the fine-grained alloys containing 9.2 and 9.5 wt% Al the value of relative elongation remains at a high level (>10%), while for the other alloys with 10–14 wt% Al it does not exceed 5%. As the content of aluminum in the alloys decreases, the character of the specimen fracture under uniaxial tension changes (from brittle to ductile).

• OSTI ID: 22943385
• Journal Information: Russian Physics Journal, Vol. 61, Issue 9; Other Information: Copyright (c) 2019 Springer Science+Business Media, LLC, part of Springer Nature; http://www.springer-ny.com; Country of input: International Atomic Energy Agency (IAEA); ISSN 1064-8887
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINIUM
ANNEALING
AUSTENITE
ELECTRON DIFFRACTION
ELECTRON MICROSCOPY
FRACTURES
GRAIN BOUNDARIES
GRAIN SIZE
MARTENSITE
MECHANICAL TESTS
PHASE TRANSFORMATIONS
QUENCHING
RECRYSTALLIZATION
SEGREGATION
SHAPE MEMORY EFFECT
TEMPERATURE RANGE 0273-0400 K
TENSILE PROPERTIES
THERMOMECHANICAL TREATMENTS
X-RAY DIFFRACTION
YIELD STRENGTH