Experimental Study the Corrosion Resistance and Wear Resistant of (Ti12Mo) alloy by Alumina particles addition Using Powder Metallurgy for Humans Implant

INTRODUCTION
Titanium and its alloys remain the traditional backbone of load-bearing biomedical implants because they combine low density, high specific strength, and excellent corrosion resistance that originates from the rapid formation of a stable passive TiO₂ film in physiological environments [1–5]. Nevertheless, widely used alloys (e.g., conventional α/α+β systems) may present a mechanical mismatch with bone due to their relatively high elastic modulus, which can promote stress shielding and long-term loosening [6,7]; therefore, modern implant metallurgy has increasingly focused on β-type titanium alloys engineered to achieve lower modulus while retaining high corrosion stability and adequate strength [8]. Among β-stabilizing elements, molybdenum is widely adopted because it strongly stabilizes the β phase and is commonly associated with improved passivation and corrosion performance in chloride-containing media [9–11], which makes Ti–Mo compositions (including Ti–12Mo-class alloys) attractive candidates for next-generation orthopedic components [12]. However, a persistent limitation of titanium alloys in demanding implant locations is their modest tribological behavior—typically low hardness and poor resistant to wear—which can accelerate material loss and increase the risk of debris-related biological complications [13]; hence, improving wear/tribocorrosion performance remains a central requirement for extending implant service life [14].
A proven pathway to address titanium’s tribological weakness is to develop titanium matrix composites by incorporating hard ceramic particulates that increase load-bearing capability at the contact interface and reduce the real area of metallic adhesion [14–16]. Alumina (Al₂O₃) is especially attractive because it is chemically inert, hard, and commonly considered compatible for biomedical use, while its incorporation can markedly enhance resistant to wear and may also modify corrosion and tribocorrosion response through microstructural and interfacial effects. Recent tribocorrosion studies on Ti–Al₂O₃ composites processed via powder routes have demonstrated that alumina additions can influence both electrochemical behavior and material degradation under combined mechanical–electrochemical loading in saline solutions relevant to physiological conditions [17].
Powder metallurgy (PM) is particularly suitable for producing Ti–Mo-based composites because it offers near-net-shape manufacturing, compositional flexibility, and the ability to distribute reinforcement particles more uniformly than many melt routes, while also enabling microstructure and porosity tailoring when required for biomedical function [18,19]. Over the last decade, PM of titanium alloys has been repeatedly highlighted as a cost-effective and technically mature pathway for structural and biomedical titanium components, with strong emphasis on its advantages in near-net-shape fabrication and property tailoring [20]. Despite these advances, the coupled corrosion–wear response of PM-processed Ti–Mo alloys reinforced with Al₂O₃ remains insufficiently established in the open literature compared with the extensive work on monolithic alloys or surface-engineered titanium. In particular, systematic experimental evidence clarifying how alumina particulates affect microstructure, densification quality, passive-film stability, and wear/tribocorrosion mechanisms in Ti–Mo matrices is still needed to guide implant-oriented material selection and processing optimization [14].
Recent studies have clearly advanced the understanding of titanium-based biomaterials; however, important limitations remain. Zhang and Chen [21] comprehensively reviewed biomedical titanium alloys and confirmed that β-type Ti alloys, including Ti–Mo systems, exhibit superior corrosion resistance and lower elastic modulus than conventional Ti alloys, yet they emphasized that poor resistant to wear remains unresolved for load-bearing implant applications. Zhou et al. [22] experimentally demonstrated that powder-metallurgy-processed Ti–Mo alloys show improved passivation behavior and reduced corrosion current density in phosphate-buffered saline as Mo amount increases; nevertheless, their work focused on monolithic alloys without addressing tribological degradation. Fang et al. [20] and Wang et al. [23] highlighted that powder metallurgy enables near-net-shape fabrication and compositional flexibility for biomedical titanium, but both studies reported that residual porosity and limited surface hardness still constrain wear performance. To overcome this, Sousa et al. [17] investigated Ti–Al₂O₃ composites produced via powder routes and showed that alumina reinforcement significantly enhances resistant to wear and modifies tribocorrosion behavior in saline media; however, their matrix systems were primarily pure Ti or Ti–Al based, not β-Ti alloys. More recently, Sousa et al. [24] further demonstrated that Al₂O₃ amount and interfacial phases strongly influence corrosion and tribocorrosion mechanisms, yet Ti–Mo matrices were not considered. Collectively, these studies reveal a clear gap: although Ti–Mo alloys are well recognized for corrosion stability and Al₂O₃ reinforcements are proven to improve resistant to wear, there is a lack of systematic experimental research integrating both strategies—specifically, the corrosion and wear behavior of powder-metallurgy-fabricated Ti–12Mo alloys reinforced with alumina particles—along with a mechanistic correlation between densification, microstructure, passive-film stability, and wear mechanisms under conditions relevant to human implants.

MATERIALS AND METHODS
The samples have been produced by powder metallurgy using Ti12Mo-xAl2O3 alloys. Table 1 provides the specimen’s mean particle size and purity level. Steel balls of various sizes were used in a revolving motorized ball mill to carefully combine the weighted powders. As a wet blending medium, ethanol has been utilized. Five hours were spent on the blending process.  An electrical hydraulic press was used to compress a 3.5-gram powder mixture of fine particles to produce a disk-shaped specimen that measured diameter=1.2 cm and thickness= 0.6 cm. Throughout compaction, 800 MPa of pressure had been used, and the specimen was kept at this pressure for four minutes. Under argon situations, the process of sintering has been carried out in an electrical argon oven. Following the compaction phase, the specimens were sintered by raising their temperature to 950 °C at a rate of 10 °C per minute. After being submerged for seven hours, the samples are cooled in the oven until they reach room temperature.

Microstructures Characterization
X-Ray Diffraction 
Following sintering, the Ti alloy was examined using X-ray diffraction, and the results had been in comparison with typical charts. With a copper (Cu) target, the test has been carried out at a speed of 6°/min, a step size of 0.02°, and with an angle ranging from 20 to 80 °. The voltage was 40 kilovolts, the current had been 30 mA, and the wavelength used had been 1.54060 Angstroms.
Microstructure Observation
Following sintering, silicon carbide sheets with different grit sizes—180, 400, 600, 800, 1000, 1200, 1500, and 2000—were used to grind all of the specimens. The last step was polishing the specimens utilizing diamond paste to get a glossy and shiny appearance. The room temperature was used for the etching process. The chemical makeup of the etching solution is shown in Table 2 [25]. The specimens were cleaned with water and dried after the etching procedure. After that, optical and scanning electron microscopy were used to examine them at 400x magnification. The examination of grain boundaries includes characteristics including grain size, shape, and phase identification. Each of them has characteristics.

Corrosion Test
In compliance with ASTM guidelines, polarization studies were carried out using an electrochemical standard cell that included a reference electrode (saturated calomel electrode) in Ringer solution, an auxiliary electrode (platinum), and a working electrode [26]. A potentiostat of the Winking M Labf200 type has been used for polarization experiments. Potentiodynamic polarization begins at an initial potential of 250 mV under the open circuit potential and proceeds to 800 mV above the open circuit potential after achieving a constant potential. The current was measured in proportion to the potential after the samples had been scanned in the positive direction at a sweep rate of 0.4 mV/s. The Eq. 1 is used to compute the corrosion rate after the test yields the corrosion current density (Icorr) and corrosion potentials (Ecorr) [26].

Whereas, E.W: equivalent weight (g/eq.), ρ: density (g/cm3), Icorr: current density (μA/cm3).

Wear Test
Pin-on-disk devices (MT-4003, version 10) are used to study dry sliding wear. 300 rpm, a constant radius of 4 mm, varying sliding distances, and loads of 10N and 20N were used in the test. An electrical scale with a 0.0001 precision is used to weigh the sample before testing. The samples are scaled at set times (5, 10, 15, 20, 25, and 30 min), and the dry sliding rate of wear is computed using Eq. 2. The test procedure was conducted in accordance with ASTM G 99 [27,28].

Whereas, ΔW= The weight loss (g) after 5, 10, 15, 20, 25, and 30 minutes, ρ (g/cm³) = final density.
The rate of wear has been determined from Eq. 3 [29]. 

Whereas, Wa refers to the rate of wear, (cm3/N.m), ΔG refers to the loss in weight, (g), ρ refers to the density of the selected materials, (g/cm3), P refers to the applied load, (N), s refers to the distance of sliding, (m).

RESULTS AND DISCUSSION
Microstructure Characterization
The observable elements in the XRD patterns of the green compact alloys are the Al2O3 phases of alumina particles, titanium (Ti), molybdenum (Mo). This is due to the fact that phase transition does not occur during the compacting process. One kind of process of diffusion that needs an elevated temperature to occur is phase transition. The XRD patterns formed by the base alloy (Ti12Mo) during sintering at 950 degrees Celsius for seven hours in an argon environment are shown in Fig. 1. Two solid solutions, αTi and βTi, were formed from Mo, and Ti.
The base alloy (Ti12Mo) with 5 percent Al2O3 XRD pattern is shown in Fig. 1 after a 7-hour sintering operation at 950 degrees Celsius in an argon gas environment. The fundamental elemental chemicals Ti, Mo, and Al2O3 are transformed into αTi, βTi, and Ti6 Al2O3 in the image. Nevertheless, there are no peaks in the image that correspond to metal Ti, Mo, and Al2O3. Because it improved the interdiffusion between Al2O3, Mo, and Ti, the 7-hour sintering procedure was enough to finish the phase transformation process. Because unbound elements have negative impacts on the body, they are prevented in alloys utilized as biomaterials.  
At a 400X magnification, the etched alloys microstructure after the process of sintering is shown in Figs. 2-4, both with and without the inclusion of Al2O3. By looking at these alloys’ microstructure, the boundaries of the grains and the current phases were determined. Following the process of sintering, the samples were discovered to have a duplex microstructure, which is made up of two separate areas. The α-Ti phase is present in one area, which looks light (bright), whereas the β-phase is present in the other parts, which seem dark. Because Mo elements stabilize the β phase, their existence causes the dark reign (β-phase) to be promoted. The darkened area rises as the number of alumina particles increases. Similar to α-β and β alloys, certain beta phases are in equilibrium at room temperature [30]. Granular boundaries, pores of different sizes, and the α-Ti and β-Ti phases are visible in the SEM images of the etched alloys, which can be seen in Figs. 2-4. A limited number of surface holes are seen by the SEM inspection because of the metal powder approach employed to prepare the sample; these pores diminish as the quantity of alumina particles rises. The material’s resistance to corrosion is improved by this decrease in porosity, which is ascribed to the function of alumina particles in altering the alloy structure. The homogeneous distribution of the reinforcing phase during the matrix produced by the powder metallurgy method improves the mechanical properties and resistant to wear of the alloys used. As shown in XRD Fig. 1, the microstructure exhibits the presence of an intermetallic phase (α-Ti - β-Ti), which improves the alloy’s mechanical characteristics and hardness as the amount of alumina particles increases. 

Corrosion Test
A single specimen of every (Ti12Mo-x Al2O3 and Ti12Mo) was used in the electrochemical corrosion process. Fig. 5 shows the anodic and cathodic polarization properties of Ti12Mo-x Al2O3 and Ti12Mo in Ringer solution at 37±1 degrees Celsius using schematic current-potential curves, sometimes referred to as polarization curves. The polarizing curves for the Ti12Mo alloy and the Ti12Mo alloy with Al₂O₃ addition are shown in Fig. 6. When cathodic polarization occurs, the voltage increases and the current decreases until it reaches the lowest possible magnitude. The voltage increases as the current increases throughout anodic polarization. The concurrent rise in voltage and current is indicative of active anodic polarization activity, which shows that the metal is still dissolving. The anodic curve’s form shows that both the Ti12Mo alloy and the Ti12Mo alloy with Al₂O₃ addition have a passive area. Fig. 6 shows the corrosion current densities, corrosion potentials, and the calculated rate of corrosion information derived from these curves.
Table 3 clearly demonstrates a pronounced and systematic enhancement in the corrosion resistance of the base Ti–12Mo alloy with increasing Al₂O₃ amount, which is closely associated with the progressive reduction in residual porosity. The corrosion resistance enhancement increases from a marginal 0.5% at 0.45 wt.% Al₂O₃ to 70. % at 1 wt.%, 75% at 1.5 wt.%, and exceeds 78% beyond 2 wt.% Al₂O₃, ultimately reaching a maximum enhancement of 98% at 5 wt.% Al₂O₃. This trend is corroborated by the electrochemical parameters, as the corrosion current density (Icorr) decreases markedly from 3.10×10-10 μA/cm2 at 0.5 wt.% Al₂O₃ to 2.23×10-12 μA/cm2 at 5 wt.% Al₂O₃, both of which are substantially lower than that of the unreinforced alloy (1.90×10-10 μA/cm2). Concurrently, the corrosion potential (Ecorr) shifts progressively toward more noble values, from −220 mV at 0.5 wt.% Al₂O₃ to −11 mV at 5 wt.% Al₂O₃, compared with −298 mV for the base alloy. The combined decrease in Icorr and positive shift in Ecorr indicate enhanced passivation behavior, which can be attributed to porosity reduction and the formation of a more compact and stable protective oxide layer on the alloy surface induced by Al₂O₃ addition, thereby effectively suppressing electrochemical dissolution and improving corrosion resistance.

Wear Test
The association between enhanced resistant to wear and a higher Al2O3% indicates that the addition of Al2O3 improves resistant to wear. The creation of the intermetallic complex (Ti6 Al2O3), which adds to the enhanced hardness of all alloys having germanium, is responsible for this occurrence. The Brinell hardness (HB) and resistant to wear enhancement % of the Ti12Moalloy in relation to the addition of Al2O3 are shown in Table 4. The rate of wear for Ti12Mo alloy is (2.20x10-6, 4.10x 10-6) (cm3/N.M) at (10N & 20N), respectively. The above statistics show that when loads of 10N and 20N are applied, the rate of wear at (20N) is higher than that of (10N) due to an increased friction coefficient. Before reaching its maximum value, the rate of wear first rises between 10N and 20N. Nevertheless, the rate of wear stabilizes and approaches a steady state as the germanium concentration rises. The surface’s decreased resistance, which makes it simpler to remove the convexity and concavity layers, is what causes the first rise in rate of wear. Until the rate of wear stabilizes, signifying the achievement of a constant coefficient of friction, this procedure is repeated.
Under constant load time and (20N and 30min), the Ti12Mo alloy and Ti12Mo alloy with Al2O3 addition rate of wear decreases with increasing Ge amount. The 0.5% Alumina particles alloy rate of wear is (2.23x10-6 cm3/N.M) compared to that of Ti12Mo alloy (4.10x10-6 cm3/N.M), achieving an enhancement rate of (48.52%).The reinforcing impact of intermetallic compounds is responsible for the resistant to wear enhancement, which rises with increasing Alumina particle concentration until it reaches 98.84% at 5% Alumina particles. By minimizing porosity and increasing the alloy’s hardness, the addition of alumina particles lowers the rate of wear. This is explained by the intermetallic compound’s (Ti6 Al2O3) reinforcing action. Fig. 6 illustrates how the amount of alumina particles affects rate of wear.

CONCLUSION
The incorporation of alumina (Al₂O₃) particles significantly enhanced the corrosion resistance of the Ti–12Mo alloys, with the enhancement exhibiting a strong dependence on Al₂O₃ amount. A maximum corrosion resistance enhancement of 98.8% was achieved at 5 wt.% Al₂O₃, corresponding to an extremely low corrosion rate of 2.14×10-10 mpy, indicating the development of a highly stable and protective passive surface layer. The resistant to wear of the Ti–12Mo alloy was markedly improved by Al₂O₃ reinforcement, with a monotonic increase observed as the alumina amount increased. The highest enhancement in resistant to wear, reaching 98.84%, was recorded at 5 wt.% Al₂O₃, where the rate of wear was reduced to 1.26 × 10-8 cm³/N·m, demonstrating the effectiveness of alumina particles in mitigating material removal under sliding conditions. The addition of Al₂O₃ particles to the Ti–12Mo matrix promoted the formation of the Ti₆Al₂O₃ intermetallic phase, which contributed to a substantial increase in hardness. As a result, the hardness of the composite reached approximately 295kg/mm² at 5 wt.% Al₂O₃, reflecting enhanced resistance to plastic deformation and improved load-bearing capability. The presence of Al₂O₃ particles also led to a pronounced reduction in residual porosity, decreasing to approximately 19.2% at 5 wt.% Al₂O₃. This densification effect played a critical role in suppressing electrolyte penetration and stabilizing the passive film, thereby contributing directly to the observed reduction in corrosion rate and overall enhancement in electrochemical performance.

CONFLICT OF INTEREST
The authors declare that there is no conflict of interests regarding the publication of this manuscript.