Experimental investigation of the effects of different quaternary elements (Ti, V, Nb, Ga, and Hf) on the thermal and magnetic properties of CuAlNi shape memory alloy

Novel Quaternary CuAlZnMg High Temperature Shape Memory Alloy (HTSMA) Fabricated by Minor Batch of Zn and Mg Additions

“…The determined parameter values of transformation temperatures and the values of some other related thermodynamic parameters hysteresis gap (As-Mf), Amax temperature, equilibrium temperature (T0), enthalpy change (ΔHM→A) and entropy change (ΔSM→A) are given in Table 1. Here, the the equilibrium temperature, T0 (calculated by using T0=(Af+Ms)/2 formula [7]) is the temperature at where the Gibbs free energy differences of two interconvertible solid (M and A) phases are equal therefore there is no any driving force to lead a martensitic transformation. Then, the entropy change amount, ΔSM→A was found by using ΔSM→A =ΔHM→A /T0 formula [7,44].…”

“…Here, the the equilibrium temperature, T0 (calculated by using T0=(Af+Ms)/2 formula [7]) is the temperature at where the Gibbs free energy differences of two interconvertible solid (M and A) phases are equal therefore there is no any driving force to lead a martensitic transformation. Then, the entropy change amount, ΔSM→A was found by using ΔSM→A =ΔHM→A /T0 formula [7,44]. As seen, the produced CuAlZnMg alloy is a high temperature shape memory alloy (HTSMA) [1,20,31,45] due to that it showed a reversible martensitic transformation at a temperature range (or simply an Af temperature) far above 100 ⁰C.…”

“…Shape memory alloys (SMAs) are crystallographically designed smart materials that can make large distorsions like martensitic phase transformation in a temperature interval region or high elastic behavior at a higher temperature region which can be triggered by application of external effects such as heat or mechanical force, and can backtrack to their original shape when external forces are removed [4,5]. These exceptional behaviors of SMAs based on martensitic phase transformation are defined as their unique properties of shape memory effect (SME) and superelasticity (SE) [5][6][7]. These versatile alloys have already been utilized for their SME, SE and some other properties in numerous applications including actuator, automotive, aerospace, medical, robotics, micro/nano electromechanical systems (M/NEMS) and photodetectors [6,[8][9][10][11][12][13][14][15][16][17][18][19].…”

“…Among these, NiTi alloys with superior shape memory properties are the most commercially used SMAs in industry and technological applications, but they are expensive and the production-processing processes are more difficult. This led researchers to pay attention on the second largest SMAs group; the Cu-based SMAs, which are regarded as the closest alternative to NiTi SMAs in terms of good SME and SE properties [7,22,23]. The most-known Cu-based SMAs such as Cu-Al-Ni, Cu-Zn-Al, Cu-Al-Mn alloy systems have been substantially studied untill today.…”

“…The main reasons for the selection of Cu-based SMA systems are the low costs, easy fabrication and also much higher heat and electrical conducivity of these alloy systems as compared to NiTi ones. But, Cu-based SMAs have some drawbacks that are tried to be improved such as thermal instabilities, martensite stabilization and brittle nature and weak mechanical properties (low cold workability) stemmed from mainly their microstructural properties such as the large grain sizes, accumulation of secondary phases or impurities along the grain boundaries, high degree of order and also high elastic anisotropy in the β-phase [7,[23][24][25]. A common and simple way to modify microstructure and reduce the grain size for improving these drawbacks and also to change characteristic martensitic transformation temperatures, SME, SE or other properties is to add some ternary, quaternary or more extra additive elements such as Ti, V, Co, Mn, Zr, Ce, Fe, Ni, B, Be, Mg, Sn or C [7,18,19,[22][23][24][26][27][28][29][30][31][32][33][34][35].…”