Transformation Behavior and Shape Memory Effect of Ni 47 Ti 44 Nb 9 Alloy Synthesized by Laser Powder Bed Fusion and Heat Treating.

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%. [ABSTRACT FROM AUTHOR]