Design of High Temperature Ti-Pd-Cr Shape Memory Alloys with Small Thermal Hysteresis

Deqing Xue,Turab Lookman,Yumei Zhou,Guojun Zhang,Ruihao Yuan,Xiangdong Ding,Jun Sun,Dezhen Xue

doi:10.1038/srep28244

Deqing Xue, Turab Lookman + Show 6 more

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https://doi.org/10.1038/srep28244

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Abstract

The large thermal hysteresis (ΔT) during the temperature induced martensitic transformation is a major obstacle to the functional stability of shape memory alloys (SMAs), especially for high temperature applications. We propose a design strategy for finding SMAs with small thermal hysteresis. That is, a small ΔT can be achieved in the compositional crossover region between two different martensitic transformations with opposite positive and negative changes in electrical resistance at the transformation temperature. We demonstrate this for a high temperature ternary Ti-Pd-Cr SMA by achieving both a small ΔT and high transformation temperature. We propose two possible underlying physics governing the reduction in ΔT. One is that the interfacial strain is accommodated at the austenite/martensite interface via coexistence of B19 and 9R martensites. The other is that one of transformation eigenvalues equal to 1, i.e., λ2 = 1, indicating a perfect coherent interface between austenite and martensite. Our results are not limited to Ti-Pd-Cr SMAs but potentially provide a strategy for searching for SMAs with small thermal hysteresis.

Highlights

Shape memory alloys (SMAs) undergo a reversible martensitic phase transformation from the high symmetry austenite (A) to low symmetry martensite (M) phase upon the influence of temperature or stress field, giving rise to the shape memory effect (SME) and superelasticity (SE), respectively[1,2]
The use of geometrically non-linear theory of martensite (GNLTM) theory to design new shape memory alloys (SMAs) requires a priori knowledge of crystal symmetry and lattice parameters, or the relationship between lattice parameters and alloying elements so that λ2 can be evaluated in advance
It is known that +ΔRand −ΔR correspond to the B2-B19 and B2-9R martensitic transformations, respectively

Summary

Introduction

Shape memory alloys (SMAs) undergo a reversible martensitic phase transformation from the high symmetry austenite (A) to low symmetry martensite (M) phase upon the influence of temperature or stress field, giving rise to the shape memory effect (SME) and superelasticity (SE), respectively[1,2]. The use of GNLTM theory to design new SMAs requires a priori knowledge of crystal symmetry and lattice parameters, or the relationship between lattice parameters and alloying elements so that λ2 can be evaluated in advance The access of those information beforehand requires a lot of experimental efforts, especially for multicomponent systems. In another words, with ΔR continuously or monotonically varying with either defect doping or thermal treatment, there must exist a point or regime where ΔR= 0. A martensitic transformation occurs without any change in resistance both on cooling and on heating, the thermal hysteresis would be expected to be zero (Fig. 1(c))

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