Ti-Mo Alloys Research Articles

Electrochemical Oxidation of Ti15Mo Alloy-The Impact of Anodization Parameters on Surface Morphology of Nanostructured Oxide Layers.

It is well-known that the structure and composition of the material plays an important role in the processes occurring at the surface. In this paper, a surface morphology of nanostructured oxide layers electrochemically grown on Ti15Mo, tuned by applying different anodization parameters, was investigated in detail. The one-step anodization of Ti15Mo alloy was performed at room temperature in an ethylene glycol-based electrolyte containing 0.11 M NH4F and 1.11 M H2O. Different anodization times (ranging from 5 to 60 min) and applied potentials (40–100 V) were tested, and the surface morphology, elemental content, and crystalline structure were monitored by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray diffractometry (XRD), respectively. The results showed that contrary to the multistep anodization of titanium foil, the surface morphology of anodic oxide obtained via the one-step process contains the nanoporous outer layer covering the nanotubular structure. What is more, the pore diameter (Dp) and interpore distance (Dint) of such layers exhibit different trends than those observed for anodization of pure titanium. In particular, at a certain potential range, a decrease in both Dp and Dint with increasing potential was observed. However, independently on the used anodization conditions, the elemental content of oxide layers remained similar, showing the amount of molybdenum at c.a. 15 wt.%. Finally, the amorphous nature of as-anodized layers was confirmed, and their optical band-gap was determined from the diffuse reflectance UV–Vis spectra. It was found that Eg is tunable to some extent by changing the anodizing potential. However, further thermal treatment in air at 400 °C resulted in the anatase phase formation that was accompanied by a significant Eg reduction. Therefore, we believe that the presented results will greatly contribute to the understanding of anodic formation of nanostructured functional oxide layers with tunable properties that can be applied in various fields.

The assisting and stabilizing role played by ω phase during the[formula omitted] twinning in Ti-Mo alloys: A first-principles insight

The ω phase is commonly observed in β-Ti alloys and plays a significant role on various properties of β-Ti alloys. Although many results about the role of ω phase on mechanical properties of β-Ti alloys have been derived from theoretical and experimental studies, the role of ω phase on deformation mechanism hitherto remains elusive and deserves to be further studied. In this work, the role played by ω phase during the 112111β twinning in Ti-Mo alloys were investigated by first-principles calculations at atomic scale. In the energy favorable interface of (112)β/(101¯0)ω, we found that partial dislocations slipping on the successive 101¯0ω planes of ω phase can lead to the formation of 112111β twin nucleus. And the twin nucleus grows inwards ω grain interior through atomic shuffle. Thus, a new twinning mechanism of 112111β assisted by ω phase was proposed. Furthermore, our calculations indicated that the appearance of ITB (interfacial twin boundary) ω phase can improve the stability of the symmetrical 112111β twin boundary (TB), which can well explain the experimental phenomenon that the ITB ω phase always accompanies the formation of 112111β twin. Finally, a probable microstructure evolution sequence was suggested, namely β matrix → β matrix + athermal ω phase → 112111¯β twin → 112111¯β twin + ITB ω phase. Our calculations provide new insights on the role played by ω phase during the twinning process of 112111β, which can deepen the understanding on the deformation behaviors of β-Ti alloys.

Low-Temperature Hydrothermal Treatment Surface Functionalization of the Ultrafine-Grained TiMo Alloys for Medical Applications.

Hydroxyapatite (HAp) is the most widely used material for bio coating. The functional layer can be produced by many methods, however, the most perspective by its utility, easy to scale up, and simplicity aspects remains a hydrothermal treatment approach. In this work, an HAp coating was produced by low-temperature hydrothermal treatment on the ultrafine-grain beta Ti-xMo (x = 23, 27, 35 wt.%) alloys. The proposed surface treatment procedure combines acid etching, alkaline treatment (AT), and finally hydrothermal treatment (HT). The uniqueness of the approach relies on the recognition of the influence of the molar concentration of NaOH (5 M, 7 M, 10 M, 12 M) during the alkaline treatment on the growth of hydroxyapatite crystals. Obtained and modified specimens were examined structurally and microstructurally at every stage of the process. The results show that the layer after AT consist of titanium oxide and phases based on sodium with various phase relations dependent on NaOH concentration and base composition. The AT in 7 M and 10 M enables to obtain the HAp layer, which can be characterized as the most developed in terms of thickness and porosity. Finally, selected coated samples were investigated in terms of surface wettability test managed in time relation, which for the results confirm high hydrophilicity of the surfaces. Conducted research shows that the low-temperature hydrothermal processing could be considered for a possible adaptation in the drug encapsulation and delivery systems.

On the hydrogen environment-assisted cracking resistance of a compositionally complex Co–Ni–Cr–Fe–Mo–Ti alloy

The hydrogen environment-assisted cracking (HEAC) behavior of a compositionally complex Co–Ni–Cr–Mo–Fe–Ti–Al alloy (MP98T) proposed for marine fastener applications was evaluated via slow-rising stress intensity testing while immersed in 0.6 M NaCl at applied potentials ranging from −1.0 to −1.2 VSCE (vs. saturated calomel electrode). Results indicate that MP98T is resistant to HEAC at applied potentials representative of cathodic protection. In particular, minimal crack growth was observed across the tested applied potential range, which represented conditions known to promote aggressive HEAC in legacy Ni-based fastener alloys, such as Monel K-500. Measurement of the diffusible hydrogen concentration (CH,Diff) of MP98T as a function of applied potential in 0.6 M NaCl suggests this improved susceptibility may be linked to a reduced efficacy for hydrogen uptake in MP98T at hydrogen overpotentials where Monel K-500 is susceptible. Specifically, the CH,Diff of MP98T at a given applied potential was consistently observed to be less than 50% of that measured for Monel K-500.

Preparation of bulk Ti[sbnd]15Mo alloy using cryogenic milling and spark plasma sintering

Gas atomized Ti15Mo alloy powder was processed by cryogenic milling. Both initial gas atomized and milled powders were consolidated by spark plasma sintering at temperatures ranging from 750 °C to 850 °C for 1 and 3 min. Microstructure of the sintered samples was studied by scanning electron microscopy (SEM), chemical contamination was determined by carrier gas hot extraction (CGHE) method and phase composition was investigated by X-ray diffraction.Cryogenic milling resulted in severe plastic deformation of initially spherical particles, changing their shape, but without a significant decrease of particle size. The milled powder achieved the full density after sintering at 750 °C, while 850 °C was required for a full densification of the initial powder. The amount of α phase was higher in the sintered milled powder, while the sintered non-milled powder contained significant amount of ω phase. It was shown that an ultrafine-grained two-phase microstructure can be produced by a combination of cryogenic milling and spark plasma sintering.

New Ti–Mo–Si materials for bone prosthesis applications

Several newly obtained titanium alloys were characterized in order to evaluate the biocompatibility and their possible application as implants. For improvement of the performances of the TiMo alloys compared to other alloys, silicon was added, targeting good mechanical and technological properties, avoiding the toxic effects for human body. Titanium is very used in medical applications, due to their extremely low toxicity and good chemical stability in different body fluids. Four Ti15MoxSi (where x = 0, 0.5, 0.75, 1.0 wt %), alloys were developed and investigated regarding microstructure, mechanical, chemical and biological behavior (in vitro and in vivo evaluation). By increasing the Si content from 0 to 1% wt., the mechanical properties of the Ti15Mo alloys were significantly improved. By increasing the Si content from 0 to 1% wt., the mechanical properties of the Ti15Mo alloys were significantly improved (about 50%) from 44.50 GPa to 19.81 GPa modulus of elasticity and the hardness values 361.28 to 188.52 HV. The cytocompatibility assessment on human line osteoblasts indicated good cell-material interactions and in vivo tests indicated a successful osseointegration, the surrounding newly bone being formed without any significant inflammatory reaction. Expression of osteopontin in the peri-implant area highlights the presence of osteogenesis and bone mineralization. Metalloproteinase-2 (gelatinase A) and metallopeptidase-9 (gelatinase B) overexpression in osteoblasts, osteoclasts and osteocytes represent the markers of normal bone remodeling. All these results suggest that the TiMoSi alloys are promising materials for orthopedics devices, since mechanical properties and biocompatibility offer conditions for applying them as biomaterial.

Open Porous α + β Titanium Alloy by Liquid Metal Dealloying for Biomedical Applications

Open porous dendrite-reinforced TiMo alloy was synthesized by liquid metal dealloying of the precursor Ti47.5Mo2.5Cu50 (at.%) alloy in liquid magnesium (Mg). The porous TiMo alloy consists of α-titanium and β-titanium phases and possesses a complex microstructure. The microstructure consists of micrometer scale β-titanium dendrites surrounded by submicrometer scale α-titanium ligaments. Due to the dendrite-reinforced microstructure, the porous TiMo alloy possesses relatively high yield strength value of up to 180 MPa combined with high deformability probed under compression loading. At the same time, the elastic modulus of the porous TiMo alloy (below 10 GPa) is in the range of that found for human bone. This mechanical behavior along with the open porous structure is attractive for biomedical applications and suggests opportunities for using the porous TiMo alloy in implant applications.

In-depth assessment of new Ti-based biocompatible materials

The objective of the research is to obtain Ti20MoxSi (where x = 0, 0.5, 0.75, 1.0 wt %) alloys using the vacuum arc remelting (VAR) methods and to consider the effects of Mo and Si on physical-chemical, biological and mechanical biocompatibility. Through microstructure analysis the dendrites, grains, sub-grains, compounds have been confirmed; Mo adding determined the main β phase apparition and by increasing the Si content the dendritic microstructure was evidenced. The modulus of elasticity decreases with the amount of Si in the Ti20Mo alloys. The MTT assessment and fluorescent microscopy performed on fibroblasts and osteoblasts cells indicated a suitable cytocompatibility of the prepared alloys. Expression of osteopontin, metalloproteinases 2 and 9 (MMP2 and MMP9) in these areas into the periosteum and peri-implant highlight the bone mineralization. Mineralization and bone remodeling suggest a good biocompatibility of the implanted material with human tissue.

Effect of Quasi-Hydrostatic Pressure on Deformation Mechanism in Ti-10Mo Alloy

The deformation mechanisms of Ti-10Mo (wt.%) alloy subjected to different quasi-hydrostatic pressure values were investigated under constrained compression using stage of high-pressure torsion apparatus. Deformation products contain {332}<113> mechanical twinning, stress-induced α″ martensitic phase and stress-induced ω phase. A volume expansion accompanied stress-induced α″ martensitic phase transformation is 2.06%. By increasing the applied pressure from 2.5 GPa to 5 GPa, the dominant deformation mechanism underwent a transition from stress-induced α″ martensitic phase transformation to {332}<113> mechanical twinning.

Microstructural and mechanical properties of Ti-Mo alloys designed by the cluster plus glue atom model for biomedical application

β-type titanium alloys are acquiring research interest in orthopaedic applications because of their exceptional properties such as moderate strength, good biocompatibility and corrosion resistance, high ductility and low elastic modulus. The study aims at designing a series of binary Ti-Mo alloys (Ti-8.71 Mo, Ti-10.02 Mo, Ti-11.78 Mo and Ti-15.05 Mo (wt%)) using the cluster plus glue atom model to design the compositions. The prediction methods such as the molybdenum equivalence, the average electron ratio and the d-electron methods were used to predict the stability of the β phase. Microstructural evolution and phases of the designed alloys were characterized using the optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffractometry (EBSD) and X-ray diffractometry (XRD), while the microhardness and tensile properties were measured using the Vickers hardness tester and tensile testing machine. The microstructure of the cast Ti-Mo alloys comprised primarily the β phase and secondary orthorhombic martensitic α″ and athermal omega (ω) phases. Their elastic moduli (96.8–70.5 GPa) decreased with the amount of Ti in the glue side and were found to be lower than the commercially available 316 L stainless steel, Co-Cr and Ti6Al4V alloys. The microhardness values of the as-cast Ti-Mo alloys decreased as the amount of Ti in the glue side decreased in the cluster formula. The tensile strength of the as-cast alloys ranges from 796.76 to 593.48 MPa with Ti-8.71 wt% Mo alloy showing the highest tensile strength owing to the amount of Ti in the glue side. The yield strength of all the designed alloys decreased as the amount of Ti atoms placed in the glue side decreased. The elongation at fracture ranged between 0.28 and 0.71%, indicating that all the designed alloys fractured in a brittle manner. The elastic admissible strain of the designed alloys (Ti-15.05 wt% Mo) was significantly higher than the conventional orthopaedic implant materials (CP-Ti, Ti6Al4V) indicating that this study is promising for the development of excellent biomedical materials.

α Phase Growth and Branching in Titanium Alloys

The morphology and spatial distribution of alpha (α) precipitates have been mapped as a function of Mo content in Ti-Mo binary alloys employing a combinatorial approach based on systematic heat-treatments carried out on compositionally graded Ti-xMo samples processed using a rapid throughput laser engineered net shape (LENS) process. The composition space spans 1.5 at% to 6 at% Mo with direct step aging at 750°C, 650oC and 600°C following a β solution treatment. Three distinct regimes of α morphology and distribution were observed. These are colony-dominated microstructures originating from grain boundary α allotriomorphs, bundles of intragranular α laths, and homogeneously distributed individual fine-scale α laths. Branching of the α precipitates was observed in all these domains in a manner reminiscent of solid-state dendritic growth. The three-dimensional features of such branched structures have been analyzed and the branching process simulated by the phase field method shows its initiation at growth ledges present at the edges of the α laths.

Nanoindentational and conventional mechanical properties of spark plasma sintered Ti–Mo alloys

The densification behavior and mechanical properties of spark plasma sintered titanium-molybdenum alloys were investigated in this paper. All Ti-(4, 8, 12, 16, and 20 wt%) Mo samples were sintered at 1200 °C for 5 min under 50 MPa. A significant relative density of 99.9% was secured for the Ti-based alloy with 16 wt.% Mo. The overall trend of hardness was similar to that of the relative density as Ti-16 wt.% Mo alloy showed the highest hardness values of 372 HV30 and 592 HV0.3 in macro (30 kg) and micro scales (300 g), respectively. Maximum ultimate tensile strength values (852 MPa at room temperature and 600 MPa at 600 ℃) belonged to the Ti-8 wt.% Mo sample. Such an observation was related to the formation of β-Ti phase and the strain-induced transformation phenomenon. The highest flexural strength of ∼2 GPa belonged to the Ti-12 wt.% Mo alloy, which may be a result of solid solution formation between Ti and Mo. Finally, average values of nano hardness, elastic modulus, and stiffness of various phases available in the samples with 12 and 20 wt% Mo were calculated through nano-indentation technique and the former specimen presented higher values in all the mentioned qualities.

Laser powder bed fusion of Ti15Mo

Ti15Mo is a generic alloy that has been around for a long time, however, it could not attain widespread applications compared to the Ti6Al4V due to the inherent limitations of the conventional methods of manufacturing the alloy. Laser powder bed fusion (LPBF) an additive manufacturing technology was used to determine the possibility of manufacturing the Ti15Mo alloy with improved mechanical properties for widespread applications. 85 ​wt% of Ti was mechanically mixed with 15 ​wt% Mo and in situ alloyed by the laser beam. The laser beam could not melt the Mo powder particles completely due to the thermophysical differences between the elemental powders. The ultimate tensile strength and the microhardness results obtained for the LPBF Ti15Mo samples were within the range of Ti15Mo alloy manufactured by conventional methods, which indicated that LPBF technology could be used to in situ alloy different elemental powders with mechanical properties comparable to samples manufactured using the conventional methods. The ductility of the LPBF Ti15Mo samples was lower than samples manufactured using conventional methods. The low ductility value was attributed to the high rate of heating and cooling simultaneously by the LPBF process.

Investigation of the tensile properties of heat treated Ti-Mo alloys

Extensive efforts have been undertaken to develop Ti alloys consisting of single β phase in order to substitute the α + β phase in Ti-6Al-4V used as biomaterials. This study was aimed at investigating the tensile properties of solution treated Ti-10Mo and Ti-12Mo alloys as a function of their deformation mechanisms. The optical microscope (OM) was used to perform microstructural analysis, while the phase identification was conducted using the X-ray diffractometer (XRD). Tensile tests were also conducted at room temperature. Results obtained show that Ti-10Mo alloy possesses higher yield strength probably as a result of stress-induced ω transformation and larger elongation due to twinning deformation than Ti-12Mo alloy. On the other hand, Ti-12Mo alloy showed moderate yield strength and large elongation due to the dominant twinning deformation mode. Both Ti-10Mo and Ti-12Mo alloys showed substantial and conspicuous equiaxed dimples, tearing ridges and few cleavage facets, which confirmed the occurrence of quasi-cleavage fracture.

The effect of solution treatment on the microstructure and mechanical properties of as-cast Ti-Mo alloys

The present study investigates the effect of solution treatment on the microstructure and mechanical properties of as-cast Ti-Mo alloys. The two alloys (Ti-8Mo and Ti-9Mo) were fabricated using a commercially available Arc re-melting furnace. Thereafter, the ingots were subjected to solution treatment and then quenched in ice water. Phase identification, microstructural analysis and fracture surfaces of both the as-cast and solution treated alloys were investigated using the X-ray diffraction (XRD) and Optical microscope (OM). The mechanical properties of both the alloys in the as-cast and solution treated state were characterized using the tensile test to obtain the elastic modulus and 3-point bend test to get the bending properties. The XRD results for Ti-8Mo alloy in as-cast and solution treated condition show dominant α″ phase peaks and Ti-9Mo alloy in as-cast condition show the dominant β phase peaks and α″ phase peaks. However, the XRD showed α″ phase peaks after solution treatment. The optical micrographs of both alloys in as-cast condition show equi-axed beta grains with sub-grain boundaries within the grains. On the other hand, the Ti-9Mo alloy show needle like structure within the beta equi-axed grains after solution treatment while the Ti-8Mo show only needle like structures without beta equi-axed grains. The fracture surfaces after tensile test in the as-cast condition display cleaved and dimple features of various sizes while the fracture surface of the alloy after solution treatment show only dimple features. The elastic modulus obtained after tensile test decreases after solution treatment. The bending strength of Ti-8Mo alloy decreased after solution treatment whereas the Ti-9Mo alloy show a significant increase in the bending strength after solution treatment.

Fabrication, mechanical property andin vitrobioactivity of hierarchical macro-/micro-/nano-porous titanium and titanium molybdenum alloys

Abstract

Electrochemical Behaviour of Ti-Mo Alloys for Medical Application in Biological Solution

Nowadays, primordial concern represent population health with all materials that are used in medical applications. It were obtained three alloys of titanium with addition of elements like molybdenum, zirconium and tantalum, in a vacuum arc melting furnace (VAR), in argon atmosphere. These alloys were investigated in biological solution, similar with to the human body by electrochemical study method (linear and cyclic polarization). Results revealed that it possesses a good behaviour which does not influence the human body, with future applications in medical field.

Origin of \u03c9-phase formation in metastable \u03b2-type Ti-Mo alloys: cluster structure and stacking fault

The ω-phase formation and its collapsed structures in metastable β-type Ti-Mo alloys were illustrated by first-principles calculations and experimental evidence of a partially collapsed ω-phase in the nano-scale Mo-depleted region under a rapid cooling via high-angle annular dark-field scanning transmission electron microscopy. The ease of ω-phase formation within -Mo-Ti-Mo- poor cluster structure was not only due to the low energy barrier in the collapse pathway, which was caused by the reduced lattice distortion, but also due to the softening of the shear modulus (G111) as a result of the small charge density difference. The most stable collapsed structure of the ω-phase strongly depended on the minimum stacking fault energy among different collapse degrees in accordance to the smallest charge density difference. Therefore, the concurrent compositional and structural instabilities of the ω-phase was attributed to the coupling effect of the cluster structure with stacking fault from the atomic and electronic basis.

The Atomic Defect Relaxation Processes in the Ti–Mo Alloys

The Atomic Defect Relaxation Processes in the Ti–Mo Alloys

Electrochemical modification of the Ti-15Mo alloy surface in solutions containing ZnO and Zn3(PO4)2 particles.

This paper reports on the plasma electrolytic oxidation (PEO) of titanium alloy Ti-15Mo in baths containing zinc to obtain biomaterials with bacteriostatic and antibacterial properties. The Ti-15Mo surface was oxidised in a 0.1 M Ca(H2PO2)2 bath containing zinc compound particles: ZnO or Zn3(PO4)2. During the PEO process, the applied voltage was 300 V, and the current density was 150 mA∙cm-2. The surface morphology, roughness and wettability were determined. It has been noted that both roughness and wettability of Ti-15Mo alloy surface increased after PEO. EDX and XPS chemical composition analysis was carried out, and Raman spectroscopy was also performed indicating that Zn has been successfully incorporated into oxide layer. To investigate the antibacterial properties of the PEO oxide coatings, microbial tests were carried out. The bacterial adhesion test was performed using four different bacterial strains: reference Staphylococcus aureus (ATCC 25923), clinical Staphylococcus aureus (MRSA 1030), reference Staphylococcus epidermidis (ATCC 700296) and clinical Staphylococcus epidermidis (15560). Performed zinc-containing oxide coatings did not indicate the bacteria growth inducing effect. Additionally, the cytocompatibility of the formed oxide layers was characterised by MG-63 osteoblast-like live/dead tests. The surface bioactivity and cytocompatibility increased after the PEO process. The zinc was successfully incorporated into the titanium oxide layer. Based on the obtained results of the studies, it can be claimed that zinc-containing PEO layers can be an interesting course of bacteriostatic titanium biomaterials development.