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In the present study, the microstructure features and martensitic transformation behaviour of a Ni-Mn-Ga alloy were tailored by adjusting the Ag content. In addition, the effect of Ag content on the thermal stability was also explored. The results revealed that the non-modulated martensite phase and Ag particles coexisted in the Ni-Mn-Ga-Ag alloys. Different martensite variants were in the {112} type I twinning relationship. With increasing Ag content, not only all transformation temperatures but also the thermal hysteresis decreased continuously in a quasilinear manner. This was attributed to the introduction of small and soft Ag particles, which were applied to release the elastic energy during the martensitic transformation. The decreasing trend of elastic energy was highly nonlinear. The alloy with 4 at% Ag addition was the percolation threshold. In addition, the relationship of energy dissipation against Ag is not monotonic. While the energy dissipation of Ni 48 Mn 25 Ga 19 Ag 8 is almost zero, the others were much higher. Furthermore, unlike others, Ni 48 Mn 25 Ga 19 Ag 8 featured good martensitic transformation stability upon thermal cycling. • A series of Ni-Mn-Ga-Ag alloys were investigated. • NM martensite plates and Ag particles were observed in Ni-Mn-Ga-Ag alloy. • Transformation temperatures and hysteresis decreased by increasing Ag contents. • Ni 48 Mn 25 Ga 19 Ag 8 exhibited good thermal cycling stability. [ABSTRACT FROM AUTHOR]

In the present study, lightweight high-strength Ti-V-Al based high temperature shape memory composites were fabricated to broaden the application of shape memory alloys. In-situ TiB whiskers and La 2 O 3 particles were introduced and the distribution of reinforcements was optimized by the combination of low-energy milling, hot-press sintering and subsequent hot rolling. The in-situ reinforcements formed a network structure, which evolved from an equiaxed shape to an ellipsoidal shape. Furthermore, the direction of the reinforcement was inclined to the rolling direction. In the reinforcement-lean area, the phase constitution evolved from the β parent phase to the α″ martensite phase, and the width of the α″ martensite gradually widened with increasing distance to the in-situ reinforcements. The composites maintained high martensitic transformation temperature characteristics. Excellent mechanical properties with a high tensile strength of 885 MPa and a large elongation of 13.1% are obtained in the composite with a 1.0 wt% LaB 6 addition and 70% deformation ratio. Meanwhile, the composite realized 3.49% recoverable strain under 6% pre-strain conditions. • (TiB+La 2 O 3)/Ti-V-Al shape memory composites were successfully prepared. • The hot-rolled process optimized the direction of the reinforcement. • The A p was changed due to different hot-rolling ratio or LaB 6 addition. • The composites realize high strength, large elongation and recoverable strain. [ABSTRACT FROM AUTHOR]