Papers by Keyword: Ti₆Al₄V Alloy

Abstract: A layer of thick oxide film was formed on Ti6Al4V substrate by anodization. Subsequently alkali and heat treatment induced to form bonelike apatite layer on its surface in SBF for 7 days. The performances of the implants in vivo were observed by naked eyes and H.E. staining technique. The bone tissues around the surface and interface of the specimen in treated Ti6Al4V group were formed more quickly than those in Ti6Al4V and 316L alloy groups. H.E staining results of treated Ti6Al4V group showed the development of newly formed bone tissues on the implant-bone interface area.

Abstract: We employed a slightly supersaturated solution (Ca/P) with an ionic composition simpler than that of simulated body fluid (SBF) to obtain a fast biomimetic coating on Ti6Al4V substrates. The results of thin film X-ray diffraction, FTIR, SEM, TEM-ED investigations indicate that hydroxyapatite (HA) nanocrystals are laid down in a few hours on the susbstrates. The amount of deposition increases with the immersion time. Furthermore, the thin layer of HA deposited after 3 h soaking in Ca/P solution acts as a catalyst for the further deposition of apatite from SBF.

Abstract: The aim of this study was to test the in vitro cytotoxicity of wood-based biomorphic Silicon Carbide (SiC) ceramics, using MG-63 human osteoblast-like cells. This innovative material has been recently developed and it exhibits unique mechanical properties towards their application in biomedical technology. In the solvent extraction test the SiC ceramic extracts had almost no effect on cellular activity even at 100% concentration. A similar behaviour was found for Ti6Al4V and bioactive glass, used as reference materials. The results of the cell morphology and the cellular attachment response have also demonstrated that the in vitro performance of these biomorphic SiC ceramics is qualitatively comparable to that produced by titanium alloy and bioactive glass, which seems very promising.

Abstract: The high temperature deformation mechanisms of two phase a+b alloy and a near-a alloy were investigated, and compared within the framework of inelastic-deformation theory. For this purpose, load-relaxation tests were conducted on the two alloys at temperatures of 750~900°C. The flow stress-vs.-strain rate curves for both alloys were well fit with inelastic deformation equations describing dislocation glide and grain boundary sliding. The amount of grain boundary sliding resistance was higher in the near-a alloy rather than the two phase a+b alloy due to difficulty in stress relaxation at triple junction region.

Abstract: The complex superplastic forming (SPF) technology applying gas pressure and compressive axial load is an advanced forming method for bellows made of titanium alloy, which forming process consists of the three main forming phases namely bulging, clamping and calibrating phase. The influence of forming gas pressure in various phases on the forming process are analyzed and models of forming gas pressure for bellows made of titanium alloy are derived according to the thin shell theory and plasticity deformation theory. Using model values, taking a two-convolution DN250 bellows made of Ti-6Al-4V titanium alloy as an example, a series of superplastic forming tests are performed to evaluate the influence of the variation of forming gas pressure on the forming process. According to the experimental results models are corrected to make the forming gas pressures prediction more accurate.

Abstract: Titanium and titanium alloys have low density, high strength, excellent corrosion resistance in many media and are known to be biocompatible. This combination of properties makes titanium and its alloys an excellent choice for the applications, such as watch parts, medical devices, dental parts and sports goods. However, in the respect of fabricating complicated shaped parts, low machinability may be a barrier to practical uses. Therefore, it is considered to be very available that metal injection molding(MIM) process is applied to fabricate titanium alloy parts[1-2]. Nevertheless, injection molding of titanium and its alloys presents a real challenge to the processor due to its reactivity. Titanium not only has a strong affinity to oxygen, but also tends to react readily with carbon, nitrogen or hydrogen from the furnace atmosphere. Therefore, contamination by interstitial light elements such as oxygen and carbon is a serious problem because they have much influence on the mechanical properties of titanium alloys[3-5]. So it is necessary to control debinding and sintering conditions. In this paper, preparation of Ti-6Al-4V compacts was performed by MIM process. To reduce the contamination, the debound compacts were sintered at moderate temperature range from 1170°C to 1320°C and high vacuum (10-3Pa). On these conditions, the mechanical properties and relative density of sintered compacts were investigated.

Abstract: The Mo surface alloying layer was prepared on Ti6Al4V substrate using the plasma surface alloying technique. The component, structure and hardness of the Mo surface alloying layer were investigated. The impact test was used to determine the fatigue behavior of the Mo surface modified Ti6Al4V. The results showed that the Mo surface alloying layer enhanced the surface strength of Ti6Al4V substrate. The Mo surface alloying layer has a duplex structure with diffusing and coating layers. The diffusing layer in which the component and hardness change gradually could enhance load-bearing capacity to the surface coating and ensure the durability of the coating. In the impact test, the Mo modified Ti6Al4V showed excellent fatigue behavior and the cohesive failure mode was observed.

Abstract: Using a CO2 laser, a process of cladding Ni-base composite coating on Ti6Al4V with pre-placed B4C and NiCoCrAlY was studied. A good metallurgical bonding coating without cracks and pores was obtained in reasonable ratios of components and low energy laser process. Morphology and microstructure of the coating were analyzed with OM, XRD, SEM and EDS. It is certain that there was a reaction between B4C and Ti during in-situ producing TiB2 and TiC. The Ni-base composite coating is strengthened with TiB2 and TiC reinforcement phases. Vickers Hardness Tester measured that the average microhardness of the coating is HV1200 and it is 3.5 times of the Ti6Al4V substrate. The high hard coating containing several reinforcement phases greatly enhances wear resistance of titanium alloy.

Abstract: Effects of microstructural and environmental factors on fatigue crack propagation behavior of welded regions of cast Ti-6Al-4V alloy were investigated. Fatigue crack propagation tests were conducted for the welded regions, which were processed by two different welding methods: gas tungsten arc (GTA) welding and electron beam (EB) welding, under various load ratios (R=0.1, 0.9) and atmosphere (air, seawater). EB weld consisting of very thin α platelets had the faster crack propagation rate than the base metal and GTA weld, regardless of load ratio and atmosphere. Fatigue crack propagation rates at high load ratio (R=0.9) were faster than those obtained at low load ratio (R=0.1) and there was no crack closure at high load ratio (R=0.9), indicating that fatigue crack propagation at high load ratio was mainly controlled by intrinsic factors such as microstructure. Fatigue crack growth resistances in seawater atmosphere were slightly lower than those in air, but showed the similar trend with variation of specimen conditions. The degrees of crack closure were almost same regardless of specimen conditions in seawater atmosphere, suggesting that the fatigue crack propagation in seawater was mainly controlled by intrinsic factors such as microstructure.