Laser powder bed fusion (LPBF) presents both opportunities and challenges with regard to the customisation of NiTi alloy properties. This paper presents a systematic study of the influence of process parameters on the superelasticity of LPBF Ni-rich Ni_51.3Ti_48.7 shape memory alloy. The findings demonstrate that NiTi alloys produced through disparate process parameters exhibit disparate phase transformation behaviours and microstructures, which in turn result in varying degrees of superelasticity. At an energy density of 166.7 to 233.3 J/mm³, LPBFed Ni-rich Ni_51.3Ti_48.7 is predominantly in the martensite phase at room temperature due to the high phase transition temperature caused by a large amount of Ni evaporation loss, and exhibits almost no superelasticity. At an energy density of 66.7 to 116.7 J/mm³, LPBFed Ni-rich Ni_51.3Ti_48.7 has less Ni evaporation loss and lower phase transition temperature. It is primarily austenite phase at room temperature, and contains nano-precipitated phases internally, thereby exhibiting excellent superelasticity. The recovery rate is in excess of 5.5% at the initial compression (up to 5.7%) and in excess of 5.0% following ten cycles (up to 5.3%). Furthermore, the lower the energy density, the smaller the stress–strain hysteresis of LPBFed Ni-rich Ni_51.3Ti_48.7, with a variation range of 1.8–3.9 mJ/mm³.

Laser powder bed fusion (LPBF) technology offers an effective approach for fabricating high-performance superelastic NiTi alloys. This study achieved Ni_51.9Ti_48.1 alloys with outstanding superelastic properties through a triple optimization design of the initial powder composition, printing process parameters, and post-processing. The phase transformation behavior and microstructure of the alloys were systematically investigated. The results indicate that as energy density increases, the size and quantity of pore defects in LPBF-fabricated Ni_51.9Ti_48.1 alloys increase, phase transformation temperatures rise, and hardness conversely decreases. Ni_51.9Ti_48.1 alloys produced at lower energy densities exhibit fewer dislocations. After annealing at 600 °C, Ni₄Ti₃ and R phases form internally, resulting in a maximum superelasticity of 6.64%. Conversely, Ni_51.9Ti_48.1 alloys produced at higher energy densities exhibited a large number of dislocations and formed subgrains after annealing at 600 °C. Additionally, due to the high void volume fraction, they demonstrated deteriorated superelasticity.

Ni₄₇Ti₄₄Nb₉ alloys were successfully fabricated by laser powder bed fusion (LPBF) technique with different laser powers. The phase transformation behavior, tensile properties and shape memory response before and after heat treating were also investigated. The Ni₄₇Ti₄₄Nb₉ LPBF alloys have good shaping properties, though a few defects were discovered. Phase transformation peaks did not appear in the as-built samples, but were observed in the heat-treated samples. The phase transformation temperatures of the heat-treated samples increase with the increase in laser power. The tension test at room temperature indicates that the LPBF samples exhibit poor tensile ductility, which may be related to the existence of pores and Ti₂Ni or Ti₄Ni₂O_x phase during the LPBF process. However, the LPBF samples after heat treating still possess good shape memory effect (with recovery strain about 7.82–8%) and relatively high reverse transformation temperature (about 36–52.6 °C) when deformed to 8%.

This work aims to clarify the influence of texture type and intensity on the shape memory effect (SME) in NiTiNb shape memory alloy (SMA) pipe joints, especially revealing the causes for the anisotropy of SME via texture changes. Three NiTiNb rods with different intensities of the {111} texture were fabricated, and their microstructures, crystalline orientation distribution functions and inverse pole figures were obtained by X-ray diffraction and electron backscatter diffraction measurements. Simultaneously, the SME was characterized by inner-diameter recoverability of the corresponding pipe joints. For a given intensity of the {111} texture, the SME of the NiTiNb pipe joints strongly depended on the expansion direction due to {111} orientation-induced anisotropy of SME. In addition, both the SME and anisotropy of NiTiNb pipe joints increased with the increased intensity of the {111} texture. Therefore, a suitable expansion direction and strong texture intensity should be considered for high SME in NiTiNb pipe joints.

As a low melting point alloy, Sn58Bi alloy plays a unique role in many fields. However, the brittleness of Sn58Bi alloy is a limitation that has to be addressed for wider applications. According to previous studies, third element addition is favorable for improved ductility, which is attributable to structure refinement. Therefore, laser beam powder bed fusion technology was adopted to prepare Sn58Bi alloy components. Additionally, the as-printed specimens presented more refined structures compared to the as-cast specimen, so they showed better plasticity. The Sn58Bi alloy showed excellent formability when specimens were prepared by LBPBF between 40–80 W. The density of specimens nearly remained stable above laser power higher than 40 W, and CT scanning could not detect internal defects, so the Sn58Bi alloy specimen was likely to be well fabricated at high laser power. Within the laser power range of 40–80 W, with the variation of laser power or scanning velocity, the laser energy density changed accordingly, and the mechanical strength of specimens was improved with the increase of laser power density. This strength change was probably related to the microstructure evolution and internal residual stress in the printing process.