Phase transformation in carbon-coated TiNi alloy, with application to the design of a prosthesis for the reconstruction of the anterior cruciate ligament.

摘要

The objective of this research is to study the effect of surface constraint on the phase transformation of a near-equiatomic nickel-titanium (50.1 at.% Ni - 49.9 at.% Ti) shape memory alloy, Nitinol. Ultra-low temperature isotropic (ULTI) carbon was vapour deposited on the shape memory alloy as part of a design of a composite prosthesis for the reconstruction of the anterior cruciate ligament.; X-ray diffraction and surface analytical techniques indicated the formation of TiC at the carbon/Nitinol interface. Differential scanning calorimetry studies showed a marked decrease in the austenitic starting (A{dollar}sb{lcub}rm s{rcub}{dollar}) and the martensitic finishing (M{dollar}sb{lcub}rm f{rcub}{dollar}) temperatures of the surface constrained alloy during phase transformation. A model that describes this phenomenon is presented.; Cross-sectional specimens of the vapour deposited ULTI carbon on Nitinol substrates were examined with transmission electron microscopy. The phase transformation of the surface constrained Nitinol was studied in-situ. It is proposed that during martensitic transformation, the last martensite plates to form were close to the constrained surface, and these are first to disappear during reverse transformation. A model to calculate the strain energy associated with the phase transformation of the surface constrained Nitinol is proposed.; The development of the composite prosthesis for the reconstruction of the anterior cruciate ligament required testing of the new material in-vivo. The objective was to study the growth of collagenous tissue on carbon coated Nitinol. Thus, Nitinol filaments on which ULTI carbon was vapour deposited were implanted in canine knees. Scanning electron microscopy examination of the harvested filaments revealed islands of reticular collagen on the surface of the carbon coated filament.