Design and Development of High-Strength and Ductile Ternary and Multicomponent Eutectoid Cu-Based Shape Memory Alloys: Problems and Perspectives

Abstract

An overview is presented on the structural and phase transformations and physical and mechanical properties of those multicomponent copper-based shape memory alloys which demonstrate attractive commercial potential due to their low cost, good shape memory characteristics, ease of fabrication, and excellent heat and electrical conductivity. However, their applications are very limited due to brittleness, reduced thermal stability, and mechanical strength—properties which are closely related to the microstructural features of these alloys. The efforts of the authors of this article were aimed at obtaining a favorable microstructure of alloys using new alternative methods of thermal and thermomechanical treatments. For the first time, the cyclic martensitic transformations during repeated quenching, methods of uniaxial megaplastic compression, or torsion under high pressure were successfully applied for radical size refinement of the grain structure of polycrystalline Cu-Al-Ni-based alloys with shape memory. The design of the ultra- and fine-grained structure by different methods determined (i) an unusual combination of strength and plasticity of these initially brittle alloys, both under controlled heat or hot compression or stretching, and during subsequent tensile tests at room temperature, and, as a consequence, (ii) highly reversible shape memory effects.

Effect of Controlled Heat Treatment and Aluminum Additions on the Strengthening of Cu–Ni-Based Alloys

“…Figure 8 shows the resulting values of the yield strength variation obtained from the evaluated compression tests, considering the 0.2% offset of deformation. In this plot, it can be observed that the yield strength value increases proportionally with the aluminum content [35]. For the as-casting samples, the following values were obtained, AB ≈ 26 MPa, AT5 ≈ 124 MPa, and AT10 ≈ 226 MPa, the former value representing a maximum increment of 5 times more than that of the unalloyed sample.…”

Smart alloy metalized novel photonic NEMS photodiode with CuAlV/n-Si/Al junction structure

“…The term on the left side of equation (1) was found as the slope value from the linear fitting of ln(Φ/T m 2 ) versus 1000/T m plot (given in figure 5) drawn for the CuAlV alloy. By substituting the determined slope value in the left side term in equation (1), the E a activation energy of CuAlV alloy was found as 125.54 kJmol −1 .…”

“…In recent years, Cu-based shape memory alloys (SMAs) [1][2][3][4], the second important SMA group in the class of smart materials family after the superior NiTi SMAs [5][6][7], were successfully utilized as thin film nanolayers of top Schottky metal contact electrodes (which were aimed to have a dynamic electro-mechanical martensite nanostructure based shape memory effect function, good electrical conductivity, and new metal work function values different than those of usual elemental metals) in the fabrication of some new high-performance silicon photodiodes [8][9][10][11][12][13][14][15][16] which can be also regarded as micro/nano M/NEMSs [17][18][19] type new devices, actuators or sensors with photonic features.…”

Investigation of the Thermal Properties of Cu-based Shape Memory Alloy

“…Therefore, Cu-based SMAs have attracted attention not only as a low-cost alternative to the mechanical applications of nitinol but also for other applications with their superior electrical and thermal conductivity and the possibility of increasing resistance [6,7]. In Cu-based alloys, the shape memory effect is strongly dependent on thermal treatments, mechanical effects, and element ratios in the structure and production methods [8][9][10][11][12][13]. Another property of Cu-based SMAs is superelasticity, which allows for high elastic deformations of up to 14%, making them suitable for storage and dissipation of mechanical energy [1,14,15].…”