Thermomechanical Behaviour of Monocrystalline Cu-Al-Be Shape Memory Alloys and Determination of the Metastable Phase Diagram

The way to control the interfacial reactions that processes during infiltration of macroheterogeneous composite materials is suggested. The idea is to combine the stable and metastable phases in the filler’s structure which dissolves at a different rate in the molten binder. To prove this approach, the structure and gas-abrasive wear of macroheterogeneous composite materials with Cu–20Ni–20Mn binder reinforced by Fe–(9.0–10.0)B–(0.01-0.2)C filler (in wt. %) cooled at 10–20 K/s or 103–104 K/s are studied. It is shown that the wear resistance of the investigated composite materials can be enhanced by accelerating interfacial reactions between the filler and the molten binder. Therefore, the composite materials produced from a rapidly cooled Fe–B–C filler show a higher resistance to gas-abrasive wear due to formation of Fe–Fe2(B,C) metastable eutectics in its structure. This eutectics crystallizes under metastable phase diagram due to the suppression of stable Fe2(B,C) phase formation and saturation of the rest of liquid by iron in the filler cooled at 103–104 K/s. As a result of rapid dissolution of the eutectics in the molten binder during infiltration, the strong adhesion at the interfaces of the composite materials is achieved which prevents the filler from spalling out under the impacts of abrasive.

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Softening of Shear Elastic Coefficients in Shape Memory Alloys Near the Martensitic Transition: A Study by Laser-Based Resonant Ultrasound Spectroscopy

Metals ◽

10.3390/met10101383 ◽

2020 ◽

Vol 10 (10) ◽

pp. 1383

Author(s):

Petr Sedlák ◽

Michaela Janovská ◽

Lucie Bodnárová ◽

Oleg Heczko ◽

Hanuš Seiner

Keyword(s):

Shape Memory Alloys ◽

Shape Memory ◽

Single Crystals ◽

Accurate Determination ◽

Martensitic Transition ◽

Elastic Coefficient ◽

Resonant Ultrasound Spectroscopy ◽

Resonant Ultrasound

We discuss the suitability of laser-based resonant ultrasound spectroscopy (RUS) for the characterization of soft shearing modes in single crystals of shape memory alloys that are close to the transition temperatures. We show, using a numerical simulation, that the RUS method enables the accurate determination of the c′ shear elastic coefficient, even for very strong anisotropy, and without being sensitive to misorientations of the used single crystal. Subsequently, we apply the RUS method to single crystals of three typical examples of shape memory alloys (Cu-Al-Ni, Ni-Mn-Ga, and NiTi), and discuss the advantages of using the laser-based contactless RUS arrangement for temperature-resolved measurements of elastic constants.

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Thermodynamic Analysis of Thermoelastic Martensitic Transformations

Materials Science Forum ◽

10.4028/www.scientific.net/msf.449-452.1325 ◽

2004 ◽

Vol 449-452 ◽

pp. 1325-0 ◽

Cited By ~ 3

Author(s):

Yinong Liu

Keyword(s):

Shape Memory Alloys ◽

Shape Memory ◽

Experimental Determination ◽

Thermodynamic Parameters ◽

Thermodynamic Analysis ◽

Martensitic Transformations ◽

Thermoelastic Martensitic Transformations ◽

The Past ◽

Concise Overview

This paper is concerned with the application of fundamental thermodynamic theories in the analysis of thermoelastic martensitic transformations in shape memory alloys, with a particular reference to polycrystalline NiTi. The discussion is delivered in two parts. The first part presents a concise overview of the fundamental theories of thermodynamics of thermoelastic martensitic transformations established in the past 30 years. The second part focuses on the principles governing the application of the theories, interpretation of the thermodynamic parameters defined in the theories, experimental determination of the parameters, and some common misperceptions and unjustified assumptions in practice concerning these parameters.

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A Three-Phase Constitutive Model for TiNiNb Shape Memory Alloys

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.97-101.660 ◽

2010 ◽

Vol 97-101 ◽

pp. 660-666

Author(s):

Jun Wang ◽

Zhi Ming Hao ◽

Ping An Shi ◽

Shao Rong Yu ◽

Wei Fen Li

Keyword(s):

Phase Transition ◽

Constitutive Model ◽

Shape Memory Alloys ◽

Shape Memory ◽

Shape Memory Effect ◽

Conventional Theory ◽

Material Parameters ◽

Three Phase ◽

The Individual

A three-phase constitutive model for TiNiNb shape memory alloys (SMAs) is proposed based on the fact that TiNiNb SMAs are dynamically composed of austenite, martensite and -Nb phases. In the considered ranges of stress and temperature, the behaviors of austenite, martensite and -Nb phases are assumed to be elastoplastic, and the behavior of an SMA is regarded as the dynamic combination of the individual behavior of each phase. Then a macroscopic constitutive description for TiNiNb SMAs is obtained by the conventional theory of plasticity, the theory of mixture, the theory of inclusion, and the description of phase transition by Tanaka. The method for determination of the material parameters is given. This constitutive model can describe the main characteristics of SMAs, such as ferrcelasticity, pseudoelasticity and shape memory effect.

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