Thermomechanical characterization of Ni-rich NiTi fabricated by selective laser melting

Abstract

This study presents the shape memory behavior of as-fabricated and solution annealed Ni 50.8 Ti 49.2 alloys fabricated using theselective laser melting (SLM) technique. Results were compared to the initial ingot that was used to fabricate powders. Optical microscopy was employed to reveal the microstructure. The shape memory effect under constant compressive stress and isothermal compressive stress cycling tests wereutilized to investigate the shape memory characteristics of theinitial ingot and fabricated alloys. It wasrevealed that theSLM method and post heat treatments can be used to tailor the microstructure and shape memory response. Partial superelasticity was observed after theSLM process. Solutionizing the fabricated samples increasedthe strength andimproved thesuperelasticity but slightly decreasedthe recoverable strain.

Nitinol Spinal Vertebrae: A Favorable New Substitute

“…NiTi monophase is, however, both flexible and rigid depending on the temperature. Superelasticity, biocompatibility, shock damping, fatigue restraint, restricted erosion, biofunctionality, wear opposition, corrosion resistance, shape memory, and stiffness similarity to the bone are some extraordinary behaviors of the Ni-Ti alloy [9,18,[24][25][26][27][28][29][30][31][32][33][34][35]. That these characteristics make it superior to other alloys qualifies Nitinol usage for making orthopaedic implants, especially for high loading/reloading regions.…”

“…Ni-Ti having 49.0 to 50.7 % Ti can be uniphase and show shape memory effect ( Figure 2). The unique SME/SE features of NiTi attributes to the thermomechanical austenite/martensite phase transformation [29,[43][44][45][46][47]. SME is produced by temperature change, while superelasticity appears at loading/unloading treatment [48,49].…”

“…Any impurity can affect both transformation temperatures and the movementlocking precipitates which substantially deteriorate the alloy performance [53]. Temperature rise alters functional features of Nitinol [29]. Favorable behaviors of the alloy depend on the exact composition of the mono-phase, as illustrated in Figure 2 [62,63].…”

“…The following titles list some common manufacturing techniques usually used for production of nonporous and porous Nitinol: -Vacuum Induction Melting [29] -Vacuum Arc Melting [29] -3D Printing [66] -PM: Powder Metallurgy [15,17,67] -HIP: Hot Isostatic Pressure [17,24,68] -SPS: Spark Plasma Sintering [17,24,68] -CS: Combustion Synthesis [15,54,69] -Injection Molding [68] AM: Additive Manufacturing [44] which includes selective heat sintering (SHS), and sintering at high temperature [15,54], selective laser melting (SLM) [29,44,67], selective laser sintering (SLS) [9], and electron beam melting (EBM) [15].…”

“…Each method has its own benefits and deficiencies. Vacuum induction melting and vacuum arc melting are two traditional methods which lead to high contaminants which feature workability reduction [29]. Combustion synthesis (CS) is a subcategory of the thermal explosion process that needs preheating.…”