Fatigue Property of Super-Elastic Ti–Ni Alloy Dental Castings

Abstract

Ti-Ni alloy is a promising material in the medical and dental fields due to its special mechanical properties, especially super-elasticity. Since dental prostheses are generally used under repetitive stress condition, fatigue properties of Ti-Ni alloy castings were investigated in this study. Ti-50.85Ni (mol%) alloy ingots were used for casting, which exhibited super-elasticity at 310 K in tensile test. Specimens were prepared with a centrifugal casting machine and a magnesia-based mold material. Fatigue test was performed at 310 K under repetitive loading condition with sine-waved load. The minimum stress was set at 0 MPa to evaluate the fatigue properties and change in residual strain. The maximum stress was set in the appropriate range considering the tensile property. Ultimate tensile strength and elongation to fracture of Ti-Ni alloy castings were 732 MPa and 10.6%, respectively, which were between those of CP-Ti and Ti-6Al-4V alloy castings. The fatigue limit of Ti-Ni alloy casting (206 MPa) was equivalent to or higher than that of CP-Ti or Ti-6Al-4V alloy. There was linear correlation between the fatigue ratios to ultimate tensile strength and the elongation to fracture for Ti-Ni alloy, CP-Ti and Ti-6Al-4V alloy castings, while Ti-Ni alloy showed high fatigue ratio to proof stress, which appears to relate to the twin deformation by stress-induced martensitic transformation. The stress-strain properties of TiNi alloy castings were evaluated to be stable, and it is possible to utilize the super-elasticity in cast dental prostheses.

Effect of operating parameters on functional fatigue characteristics of an Ni-Ti shape memory alloy on partial thermomechanical cycling

“…Fractographic analysis was done on the fractured sample, which was heated closer to A f temperature, using a scanning electron microscope in the secondary electron mode at various magnifications, as shown in Figure 11(a) to (d). During cycling, the specimen underwent necking after a specified number of cycles and failed in a typical ductile fracture mode, that is, cup-and-cone fracture (Kasuga et al, 2005; Robertson et al, 2012). The nucleation of voids followed by growth lead to the fracture, and the signature of the coalescence of voids can be seen in the fractographs, as illustrated in Figure 11(c) and (d).…”

Fatigue Property of Ti-5Al-13Ta Alloy Dental Castings in 0.9% NaCl Solution

“…29) To evaluate the influence of the tensile properties on the fatigue limit for CP-Ti, Ti-6Al-4V, Ti-6Al-7Nb, and Ti-5Al-13Ta alloys, fatigue ratio, the ratio of fatigue limit to ultimate tensile strength, was calculated and compared with fracture elongation. Figure 4 shows the relation between the fatigue ratio and the elongation for CP-Ti, Ti-6Al-4V, Ti-6Al-7Nb, and Ti-5Al-13Ta alloys.…”

Bending Property of Super-Elastic Ti-Ni Alloy Dental Castings with Different Heat Treatments

“…[15][16][17] Dental prostheses are used under repetitive stress conditions and studies of the fatigue property of Ti-Ni alloy castings showed superior fatigue property in a placementand-removal test 18) and a tensile test. 19) It was also reported that heat treatment of Ti-Ni alloy castings improved superelasticity in a tensile test, and decreases in apparent proof stress and residual strain were observed. 20) However, in order to evaluate the mechanical properties of dental cast retainers from the clinical viewpoint, bending property is thought to be one of the suitable parameters of clinical performance considering the direction and condition of the applied force on the retainers.…”