Influence of thermo-mechanical treatment on mechanical properties and shape memory effect of CuAlNiMnTi shape memory alloys

In the present work, a comparative study of the shape memory and thermo-mechanical behaviour of four alloys containing different amount of samarium have been carried out at a strain rate of 0.08 × 10-6s-1. After hot rolling, annealing and solution treatment, the alloy samples were tensile deformed at room temperature from 1% to 5% and were then recovered at 600 °C for 20 minutes repeatedly for six times to complete six training cycles. It is found that thermo-mechanical treatment (training) results in improvement of shape memory effect and has a significant influence on mechanical parameters like proof stress (σ: 0.002), critical stress (σ: 0.0008) and strain hardening exponent. The improvement in shape memory effect by thermo-mechanical treatment can be regarded as the effect of reduction in the values of proof stress and critical stress during training which facilitates the formation of ε (martensite). It has also been noticed that excessive training may result in the formation of ά (martensite) due to continuous softening of the alloy during training, thus degrading the shape memory effect. Finally, it has also been noticed that the addition of samarium increases the values of proof stress, critical stress and strain hardening exponent. Although the addition of samarium increases the values of proof stress, critical stress and strain hardening exponent yet it has not an adverse effect on shape memory effect. In this paper, the effect of thermo-mechanical treatment on mechanical parameters such as proof stress, critical stress, strain hardening exponent and their influence on shape memory effect is discussed.

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Effect of Sm Doping on the Microstructure, Mechanical Properties and Shape Memory Effect of Cu-13.0Al-4.0Ni Alloy

Materials ◽

10.3390/ma14144007 ◽

2021 ◽

Vol 14 (14) ◽

pp. 4007

Author(s):

Qimeng Zhang ◽

Bo Cui ◽

Bin Sun ◽

Xin Zhang ◽

Zhizhong Dong ◽

...

Keyword(s):

Mechanical Properties ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Strengthening Effect ◽

Face Centered Cubic ◽

Compressive Fracture ◽

Fine Grain ◽

Fine Grain Strengthening ◽

Face Centered

The effects of rare earth element Sm on the microstructure, mechanical properties, and shape memory effect of the high temperature shape memory alloy, Cu-13.0Al-4.0Ni-xSm (x = 0, 0.2 and 0.5) (wt.%), are studied in this work. The results show that the Sm addition reduces the grain size of the Cu-13.0Al-4.0Ni alloy from millimeters to hundreds of microns. The microstructure of the Cu-13.0Al-4.0Ni-xSm alloys are composed of 18R and a face-centered cubic Sm-rich phase at room temperature. In addition, because the addition of the Sm element enhances the fine-grain strengthening effect, the mechanical properties and the shape memory effect of the Cu-13.0Al-4.0Ni alloy were greatly improved. When x = 0.5, the compressive fracture stress and the compressive fracture strain increased from 580 MPa, 10.5% to 1021 MPa, 14.8%, respectively. When the pre-strain is 10%, a reversible strain of 6.3% can be obtained for the Cu-13.0Al-4.0Ni-0.2Sm alloy.

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Effect of Cr additions on the phase constituent, mechanical properties, and shape memory effect of near–eutectoid Ti–4Au towards the biomaterial applications

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2021.159037 ◽

2021 ◽

Vol 867 ◽

pp. 159037

Author(s):

Wan–Ting Chiu ◽

Takuya Ishigaki ◽

Naoki Nohira ◽

Akira Umise ◽

Masaki Tahara ◽

...

Keyword(s):

Mechanical Properties ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Phase Constituent

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Enhancement of mechanical properties and shape memory effect of Ti–Cr–based alloys via Au and Cu modifications

Journal of the Mechanical Behavior of Biomedical Materials ◽

10.1016/j.jmbbm.2021.104707 ◽

2021 ◽

pp. 104707

Author(s):

Wan–Ting Chiu ◽

Kaoru Wakabayashi ◽

Akira Umise ◽

Masaki Tahara ◽

Tomonari Inamura ◽

...

Keyword(s):

Mechanical Properties ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect

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On the impact of lattice parameter accuracy of atomistic simulations on the microstructure of Ni-Ti shape memory alloys

Modelling and Simulation in Materials Science and Engineering ◽

10.1088/1361-651x/ac3b9e ◽

2021 ◽

Author(s):

Lorenzo La Rosa ◽

Francesco Maresca

Keyword(s):

Molecular Dynamics ◽

Shape Memory Alloys ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Lattice Parameter ◽

Lattice Parameters ◽

Atomistic Simulations ◽

Interatomic Potentials ◽

The Impact

Abstract Ni-Ti is a key shape memory alloy (SMA) system for applications, being cheap and having good mechanical properties. Recently, atomistic simulations of Ni-Ti SMAs have been used with the purpose of revealing the nano-scale mechanisms that control superelasticity and the shape memory effect, which is crucial to guide alloying or processing strategies to improve materials performance. These atomistic simulations are based on molecular dynamics modelling that relies on (empirical) interatomic potentials. These simulations must reproduce accurately the mechanism of martensitic transformation and the microstructure that it originates, since this controls both superelasticity and the shape memory effect. As demonstrated by the energy minimization theory of martensitic transformations [Ball, James (1987) Archive for Rational Mechanics and Analysis, 100:13], the microstructure of martensite depends on the lattice parameters of the austenite and the martensite phases. Here, we compute the bounds of possible microstructural variations based on the experimental variations/uncertainties in the lattice parameter measurements. We show that both density functional theory and molecular dynamics lattice parameters are typically outside the experimental range, and that seemingly small deviations from this range induce large deviations from the experimental bounds of the microstructural predictions, with notable cases where unphysical microstructures are predicted to form. Therefore, our work points to a strategy for benchmarking and selecting interatomic potentials for atomistic modelling of shape memory alloys, which is crucial to modelling the development of martensitic microstructures and their impact on the shape memory effect.

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