Shape memory characteristics of dual-phase Ni–Mn–Ga based high temperature shape memory alloys

Superelasticity in Polycrystalline Ni-Mn-Ga-Fe Microwires Fabricated by Melt-extraction

“…As a result, the critical stresses for the phase transformation kept intact. 15 ), but close to that in polycrystalline Ni-Mn-Ga microwires (~2.7%) [4] . The maximum strain that can be achieved in polycrystalline Ni-Mn-Ga-Fe microwires is limited by the intergranular fracture during loading-unloading cycles.…”

“…Such behavior has also been found in Cu-based SMAs 18 . The maximum recoverable ratio in Ni-Mn-Ga-Fe microwires is ~95.6% at 315 K as described in Figure 4b, which is much higher than Ni-Mn-Ga alloys (~63%) [15] and comparable to Ni 49.5 Mn 28.6 Ga 21.5 microwire 4 . It can be seen from Figure 4b that the strain recovery ratio increases with temperature and the residual strain decreases from 0.45% at 306K to 0.05% at 315 K. The higher recovery ratio at higher temperatures may be attributed to the higher density of elastic energy accumulated in the substrate during the process of SIMT 1 .…”

“…The brittleness of Ni-Mn-Ga alloy might be effectively improved by doping fourth transitional elements such as Fe [6][7] . A recent report revealed that the brittleness and SME of Ni-Mn-Ga alloys were significantly improved through Fe-doping 15 . Moreover, grain refinement by rapid solidification technology is also an effective way to improve the SME and brittleness 4,16,17 of Ni-Mn-Ga alloys.…”

Mössbauer Spectroscopy Studies on Magnetic Properties for 57Fe-substituted Ni-Mn-Sn Metamagnetic Shape Memory Alloys

“…Umetsu [12,13]. Substitution of Fe for Mn has to be known to enhance the ductility of Ni-Mn-Ga and Ni-Mn-Sn alloys, and the way is significantly effective for the applications [14,15]. Furthermore, the phase diagrams of Ni 2 (Mn,Fe)Ga and Ni 2 (Mn,Fe) 1.48 Sn 0.52 open question to behavior of the concentration dependence of T M because it has been thought that the variation of T M follows the general rule related to the number of the valence electrons.…”

Destabilization of Ni–Mn–Ga martensite: Experiment and theory

“…Different aspects of these alloys have been already studied. Such studies mainly concerned the basic characteristics of MT in their interrelation with the alloy composition and microstructure [3,[7][8][9][10]14] (including the addition of a forth element [18]), aging [15,17], and atomic ordering [16]. A number of reports about the compressive stressstrain tests of single crystals and polycrystalline Ni-Mn-Ga HTSMAs, showing improved plasticity, good shape recovery and thermal cycling stability, have been already presented [5,7,11,13,14,17].…”