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The two-way shape memory effect with reversible compressive strain up to 5.1% and high cyclic stability is obtained for Ni44Fe19Ga27Co10 (at.%) single crystals by stress-induced martensite aging at 398 K for 1–3 h, under 650 MPa. 100 cycles of thermal treatment at temperatures not exceeding aging temperature, do not affect the temperature of the martensite formation, and reversible strain reduces merely by 0.4%. Thermal cycling with aging overheating significantly decreases reversible strain down to 1% due to the austenite stabilization. [ABSTRACT FROM AUTHOR]

The present study investigates the high-temperature shape memory effect (SME) in heterophase Ni50.3Ti32.2Hf17.5 polycrystals with nanosized H-phase particles after stress-induced martensite (SIM) aging in tension and compression. SIM aging created the conditions for fully reversible two-way SME with a strain of up to 50% of the one-way shape memory strain. SIM aging altered the viscoelastic properties of material, in particular, the elastic moduli of austenite and martensite increased, as did internal friction. Increased interface mobility is suggested as the reason for internal friction growth. [ABSTRACT FROM AUTHOR]

Results of investigations of the two-way shape memory effect (TWSME) and its stability during stress-free thermal cycling of [001]-oriented Ni49Fe18Ga27Co6 single crystals after high-temperature isothermal training (100 loading/unloading cycles at a temperature of 373 K) in superelasticity (SE) conditions during L21-L10 martensitic transformations (MT) are presented. A maximal reversible strain of single crystals aged at 673 K for 4 h with 3.8% TWSME has been obtained. For crystals after stress-free aging at 673 K for 4 h, the TWSME is 2.2%. It has been established that on the one hand, the high-temperature training at 373 K, in comparison with analogous training at a low temperature of 295 K of stress-assisted aged crystals causes the maximal TWSME to decrease by 1.7%, and on the other hand, it promotes the increase of the cyclic stability of TWSME during reversible strain. The influence of the isothermal training temperature on the TWSME mechanism and on its degradation during stress-free cooling/heating cycles is discussed. [ABSTRACT FROM AUTHOR]

Special features of L21-(14М)-L10 martensitic transformations (MT) are experimentally established for [001]-oriented Ni54Fe19Ga27 (аt.%) single crystals under tensile stress, including staging of superelasticity curves, stress hysteresis, and strain level of martensite formation depending on the test temperature and MT sequence. An additional stage of inelastic strain with high strain hardening coefficient and a stress drop arise on the σ(ε) curves in the interval of changes of the stress-induced MT sequence from L21-14M-L10 to L21-L10 (320-400 K) at superelasticity (SE). Special features and physical reasons of this stage and of the stress drop related with the processes of origin and detwinning of L10 martensite during stress-induced L21-L10 transformation are established. The stage of inelastic strain and the stress drop are absent at the L21-14М-L10 MT in the [001]-oriented single crystals or at the L21-L10 MT at other orientations, where detwinning of L10 martensite is suppressed by geometrical reasons. [ABSTRACT FROM AUTHOR]

Using single-crystal Ni 54 Fe 19 Ga 27 (at.%) specimens, the effects of heat treatment, annealing at the temperatures within T = 473–1473 K for one hour followed by quenching into water, on the development of thermoelastic L21-L10 martensitic transformations is investigated. It is found out that using proper heat treatment modes one can control the temperature of L21-L10 martensitic transformations, the value of the temperature hysteresis, the critical stresses of twin boundary motion, and certain functional properties of single-crystal Ni-Fe-Ga. [ABSTRACT FROM AUTHOR]

Alloxan diabetes (sucrose blood concentration greater than or equal to 14 mmol/l) induced lymphocytopenia in noninbred male mice, resulting from the decrease in the number of both T and B lymphocytes differentiated by their reaction to acid phosphatase. At the same time thymic bone marrow lymphopoiesis in mice with diabetes was depressed. Nodular and splenic lymphopoiesis remained virtually unchanged. These disturbances became apparent on the 3rd week after diabetes induction. Alloxan itself has no inhibitory effect on lymphopoiesis.