Fabrication of porous NiTi shape memory alloy for hard tissue implants by combustion synthesis

AbstractPorous NiTi shape memory alloy (SMA) with ideal pore characteristics and high strength for hard tissue implants has been fabricated bycombustion synthesis in this paper. Microstructure and mechanical properties of the product were studied by optical microscope, scanningelectron microscope (SEM), X-ray diffraction (XRD) and compression test respectively. The experimental results show the combustiontemperature of Ni + Ti reactant system using an improved ignition technique can reach 1310 ◦ C at the pre-heating temperature of 350 ◦ C.Porous NiTi SMA with three-dimensionally interconnected pores has the isotropic pore structure, whose general porosity is about 57.3vol.%and the open porosity ratio is about 86%. Besides two second phases (Ti 2 Ni and Ni 4 Ti 3 ) in small amount, the desired products, such asB2(NiTi) and B19 (NiTi) are the predominant phases in porous NiTi SMA. The undesired Ti 2 Ni phase as discrete precipitates formed duringthe SHS process is often present on or near grain boundaries and difficult to be removed by solution treatment. Porous NiTi SMA has ahigh compressive strength (208MPa) and a low Young’s modulus (2.26GPa), which is similar to natural bones and can meet the mechanicalproperty demands of hard tissue implants for heavy load-bearing applications.© 2003 Elsevier B.V. All rights reserved.

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