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The NiTiHf-Nb alloy exhibits good workability as well as high-temperature shape memory property. In this work, effects of cooling rate on martensitic transformation behavior and shape memory property for Ni-rich (Ni50.1Ti34.9Hf15)85Nb15 alloy were investigated. For comparison, the martensitic transformation behavior and shape memory property of Ni50.1Ti34.9Hf15 alloy were also investigated. As the cooling rate decreased from water cooling to furnace cooling after solution treatment, the martensitic transformation temperatures (TTs) of (Ni50.1Ti34.9Hf15)85Nb15 alloy decreased gradually, whereas the decrease was not obvious for Ni50.1Ti34.9Hf15 alloy. The increased valence electron concentration (cv) should account for the decrease in TTs of (Ni50.1Ti34.9Hf15)85Nb15 alloy. The shape memory effect strain increased with the decrease in the cooling rate for both two alloys, and the largest shape memory effect strain of 2.6% can be obtained in furnace-cooled (Ni50.1Ti34.9Hf15)85Nb15 alloy. This enhancement in the shape memory property should be ascribed to the precipitation of H-phase in furnace-cooled (Ni50.1Ti34.9Hf15)85Nb15 alloy.

Recently years, hydrogels have received increased attention due to their promising applications in wound dressing, tissue engineering, biosensors and human-machine interfaces. However, designing hydrogels with good mechanical strength and self-healing ability remains a challenge. As a novel strategy, functional Janus nanosheets (JNs) were used as reinforcement to develop self-healing nanocomposite hydrogels. Herein, the silica Janus hollow spheres were prepared by a sol-gel process, modified with poly(2-(acryloyloxy)ethyl ferrocenecarboxylate)(PMAEFc)/polydopamine(PDA) to the internal/external surfaces and then crushed to fabricate the SiO2@PMAEFc/PDA JNs. The SiO2@PMAEFc/PDA JNs were then used as robust reinforcement to design self-healing nanocomposite hydrogels. Based on multiple effects of metal–coordination and host–guest interactions, the mechanical strengths and self-healing properties of hydrogels were both enhanced. Specially, after introducing JNs, the rupture stress of hydrogels increased from 1.27 MPa to 2.23 MPa, and the self-healing efficiency improved from 66.7% to 92.4%. These results demonstrate that JNs can be used as robust reinforcement to fabricate self-healing nanocomposite hydrogels, which enriches the design of self-healing hydrogels and broadens the application prospects of Janus nanomaterials.

The evolution of phase composition and microstructure such as grain size, dislocation and crystallographic texture in austenite-martensite duplex Ni47Ti44Nb9 rolled sheets during the annealing was systematically investigated. The influence of annealing temperature on shape memory effect was also examined. The strong {001} fiber texture tested in as-rolled sheets is identified as a wrong result, which is mistakenly introduced by X-ray Diffractometer, due to the interference of martensite. Different annealing temperatures result in variation of phase composition and microstructure. For instance, in the case of 600 °C, the phase fraction of austenite increases and the dislocations develop to form tiny sub-grains due to reverse martensitic phase transformation and recovery. The texture of NiTi austenite mainly concentrates on {111}〈110〉. In the case of 950 °C, the sub-grains develop to trigger recrystallization, resulting in larger grains and decreasing of dislocations and {111}〈110〉 texture intensity. In addition, the sheets annealed at 600 °C possess higher recoverability than those of 950 °C, which can be attributed to the combined role of grain size, dislocation and crystallographic texture.

The hot working behavior of Mg-Gd-Y-Nb-Zr alloy was investigated using constitutive model and hot processing maps in this work. Isothermal compression tests were conducted with temperature and strain rate range of 703–773 K and 0.01–5 s −1 , respectively. Improved Arrhenius-type equation incorporated with strain compensations was used to predict flow behavior of the alloy, and the predictability was evaluated using correlation coefficient, root mean square error and absolute relative error. Processing maps were constructed at different strains for Mg-Gd-Y-Nb-Zr alloy based on dynamic materials model. The processing maps are divided into three domains and the corresponding microstructure evolutions are referred to the forming of straight grain boundaries, twinning, dynamic recrystallization and grain growth. Instability occurred mainly at the strain rate range of 0.3s −1 –0.5s −1 . The optimum processing domain is mainly at the temperature range of 703–765 K with the strain rate range of 0.01–0.1 s −1 .