Effect of Solution Treatment on the Shape Memory Functions of (TiZrHf)50Ni25Co10Cu15 High Entropy Shape Memory Alloy

Abstract

This study investigated the effects of solution treatment at 1000 °C on the transformation behaviors, microstructure, and shape memory functions of a novel (TiZrHf)50Ni25Co10Cu15 high entropy shape memory alloy (HESMA). The solution treatment caused partial dissolution of non-oxygen-stabilized Ti2Ni-like phase. This phenomenon resulted in the increment of (Ti, Zr, Hf) content in the matrix and thus increment of the Ms and Af temperatures. At the same time, the solution treatment induced a high entropy effect and thus increased the degree of lattice distortion, which led to increment of the friction force during martensitic transformation, resulting in a broad transformation temperature range. The dissolution of the Ti2Ni-like phase also improved the functional performance of the HESMA by reducing its brittleness and increasing its strength. The experimental results presented in this study demonstrate that solution treatment is an effective and essential way to improve the functional performance of the HESMA.

Microstructure Formation in Cast TiZrHfCoNiCu and CoNiCuAlGaIn High Entropy Shape Memory Alloys: A Comparison

“…It should be noted that following the first HESMA breakthrough described in References [14][15][16][17] [15,16]. Yet, quite significant remnants of Ti 2 Ni like precipitates were observed in the microstructure after solution treatment [24,25]. The present findings clearly show the inevitability of such precipitations as interdendritic regions are provide template-like sites for those precipitates.…”

“…Obviously, such precipitations will affect the functional properties as it was shown already for the TiNi binary system. The authors of References [24,25] Amongst other possible reasons for such behavior might be the presence of precipitates. It is clear that simple solution treatments cannot fully avoid their formation.…”

“…Such chemical inhomogeneity is well known for cast HEA (e.g., [1] (p. 300), [2] (pp. [24][25], [3] (pp. 78-112), [13] (pp.…”

Structure and Properties of Coatings Made of High-Entropy Alloy with Martensitic Transformations Obtained by HVOF Method in a Protective Atmosphere

“…The dependence of the microhardness HV0.1 of the coating on the thickness (δ) is described by Equations (3) and (4). Equation (3) corresponds to curve 1, Figure 7, and Equation 4…”

“…Most of the HEA studies are focused on the structure of alloys, microstructural and mechanical properties [1]. However, few works are devoted to TRIP-effect [2][3][4] in these alloys. Alloys with shape memory effect (SME) have high strength, unique effects of single and multiple reversible thermomechanical memory, high level of reactive stresses, recovery and damping, high corrosion resistance and cyclic durability.…”