Papers by Keyword: β Titanium Alloy

Abstract: The results of the investigation of the supersaturation temperature - in the range 800÷1050°C - influence on changes in the microstructure and hardness of the Ti24Nb4Zr8Sn alloy. The microstructure analysis was performed by means of the light microscope Axiovert 200MAT of the Zeiss Company. At the supersaturation temperature of 950°C examinations were performed by means of the scanning electron microscopy (SEM), while the occurring phases were identified by using X-ray phase analysis method. Tin precipitates of a high dispersion were found in the phase β matrix. Along with the decreasing cooling rate of the alloy, from a temperature of 950°C, none essential changes in the microstructure were noticed (only a small hardness decrease). Hardness measurements were carried out by means of the Vickers apparatus, type HP0 250. It was shown that within the tested supersaturation temperatures the hardness is within a narrow range 216÷246 HV, while the average diameter of a flat grain of the primary β phase increases more than twice.The obtained results will be used at elaborating ageing parameters of the Ti24Nb4Zr8Sn alloy. In future, they can be also useful at designing chemical compositions, microstructures and heat treatment technologies of new, single-phase alloys on the titanium matrix.

Abstract: The TiO₂ nanotube array film was synthesized on the surface of Ti-Nb-Zr-Mo βTitanium alloy via anodic oxidation in single electrolytic solution only containing HF. The diameter of TiO₂ nanotubes was 30-50nm, and the length was 240nm. Compared with the processing parameters (including anodizing voltage, reaction time, concentration and kinds of electrolytic solution) used for pure Titanium or Ti-6Al-4V alloy, the parameters was further optimized. The surface morphology and element compositions Ti-Nb-Zr-Mo alloy before and after anodic oxidation were observed and analyzed by a scanning electron microscope (SEM) and an energy dispersive X-ray (EDX) spectrometer. The antibacterial property of TiO₂ nanotube array film prepared with optimal conditions was evaluated by coculture in vitro between Actinomyces viscosus and materials tested. The results indicated that the TiO₂ nanotube array film had very good antibacterial activity to resist Actinomyces viscosus. TiO₂ nanotube array film/Ti-Nb-Zr-Mo βTi alloy biocomposite will be an more excellent dental implant owning good biomechanical adaptability, biocompatibility and antibacterial property.

Abstract: Machining of Ti25Nb3Mo3Zr2Sn beta titanium alloy is carried out under two different heat treatments, solution treated, and solution treated and aged conditions. The chips formed after machining were cold mounted, polished and etched to reveal their microstructures. Different chip parameters such as average chip thickness, shear angle, undeformed chip length, and distance between serrations were measured and reported for both the heat treated samples for a wide range of cutting speeds, ranging from 5 m/min to 175 m/min. The results obtained were explained in terms of the heat treatment (hardness) of the samples and the cutting speeds.

Abstract: A constitutive model using dislocation density rate as an internal state variable has been proposed for hot working of β titanium alloy in this paper. The β phase was only taken into consideration during high temperature deformation. The solution strengthening and dislocation interaction were included in the constitutive equations. The strength coefficient was determined by equivalent vanadium content, V_eq, which was calculated according to the alloy constituent. A Kocks-Mecking model was adopted to describe the variation of dislocation density. The constitutive relationship of a β titanium alloy Ti-10V-4.5Fe-1.5Al for high temperature deformation was established using the internal-state-variable based model. Model parameters were determined by the genetic algorithm based objective optimization method. The predicted results agree fairly well with the experimental value.

Abstract: In this study the effects of different aging heat treatments on the properties and microstructure of a high strength, high toughness metastable β Ti, BTi-6554 (Ti-6Cr-5Mo-5V-4Al), have been compared. An initial β phase solution treatment was followed by aging at moderate temperatures in the α/β dual phase zone by either step aging directly from the solution treatment temperature or by quenching to room temperature prior to the aging heat treatment. The differing heat treatment methods have significant effects on the microstructure and mechanical properties.

Abstract: The effect of HIPping on the mechanical properties and microstructure of a cast Ti-6Cr-5Mo-5V-4Al alloy have been investigated. In the cast condition, the alloy predominantly consists of coarse β grains. In comparison to the HIPped samples, it exhibits poor mechanical properties, in particular low ductility, due to large amounts of remnant porosity. HIPping at 740°C substantially reduces the amount and size of porosity, while HIPping at 820°C and 900°C virtually eliminates all porosity, significantly improving the mechanical properties.

Abstract: The effects of trace boron on microstructure and mechanical properties of β type Ti-9V-3Al-3Cr-3Zr-3.5Mo (wt. %) alloy have been investigated in this study. Upon the addition of 0.02 wt. % boron, the grain size of the B-modified alloy was almost four times smaller than that of the B-free alloy. Accordingly, the tensile strength and elongation of B-modified alloy increased from 712 MPa and 14.6 % to 813 MPa and 17.9 %, respectively, mainly due to the effect of grain refinement.

Abstract: The microstructure and mechanical properties of a cast near β type titanium alloy, Ti-25Nb-3Zr-3Mo-2Sn, have been investigated in this paper. In the as cast condition, the alloy possesses coarse, equiaxed β grains and Transmission Electron Microscopy(TEM) observations showed the ω phase is also present in this condition. The alloy in the as cast condition has low strength and is highly ductile. Direct ageing at 450°C for 4 hours leads to the formation of a large number of fine scale α phase precipitates. The alloy in the aged condition is less ductile but exhibits significantly enhanced strength.