چكيده به لاتين
Nitinol (NiTi) intermetallic compound belongs to the family of shape memory- alloys. This widely used material has unique properties such as biocompatibility, superelasticity, good corrosion and abrasion resistance, which makes it distinguished it from the other shape-memory materials The most common applications of this alloy in medical engineering are in the manufacture of orthodontic wires, orthopedic implants and guide wires in cardiovascular surgery. Production of orthopedic implants requires porous structures and bone-like tissue. In the present study, sodium chloride, phenylethane, and sawdust (wood chips) were used as space holders during the combustion synthesis process to produce porous NiTi alloy. The powder mixture of nickel and titanium with equiatomic ratio after weighing was mixed with space holder materials in 50vol% and cold pressed in a steel die with uniaxial 150kN pressure. Combustion synthesis of compressed cylindrical samples was performed in induction furnace under argon gas atmosphere. The effect of space holder type on the percentage, distribution, and size of porosity, the microstructure and phases formed, and the mechanical properties of the synthesized samples were investigated. scanning electron microscopy equipped with X-ray energy diffraction (EDS) spectroscopy and X-ray diffraction (XRD) analysis used to examine specimens' microstructure and phases. The sample's porosity percentage without the space holder was 29.92% and increased to 51.65%, 36.31%, and 37.13%, using sodium chloride, phenylethane, and sawdust spacers, respectively. Among the spacers used, sodium chloride can create more controlled porosity in the structure, and the size of porosities can be adjusted by changing the size of sodium chloride. The microstructure of the synthesized sample without the space holder consisted of the NiTi, NiTi2, Ni3Ti, and Ni4Ti3, and the addition of the sodium chloride did not change the phases. The Young's modulus and compressive strength of the synthesized sample without space holder were 0.4 GPa and 59.7 MPa, respectively, which with the addition of sodium chloride particles decreased to 0.2 GPa and 25.5 MPa.
