Al-Mo Alloys Research Articles

Evaluations of Mechanical Properties and Functionalities of the Al- and Zr-Tailored Ti–5.5Mo Shape Memory Alloys for Biomedical Applications

AbstractDue to the critical world population aging issue, biomaterials are important topics in the biomedical community. Among the biomedical materials, shape memory alloys (SMAs) are considered to be promising materials owing to their functionalities, such as shape memory effect (SME) and superelasticity (SE). Ti–Mo–Al-based alloys, which are biocompatible materials, are basic materials in the Ti-based SMAs due to the evaluation of the phase stability through the calculations of Mo and Al equivalents. This study, in addition, introduced Zr into the Ti–Mo–Al-based alloys for its highly biocompatibility and being a fine modifier to tune the phase stability. The mechanical (i.e., strength and elongation) and functional (i.e., SME and SE) properties have been investigated in this study to reveal the practicability of the biomedical applications for human usage. It was found that addition of Zr to the Ti–Mo alloy shows slight influence on the mechanical properties of the binary Ti–Mo alloy. With the addition of Al, that is, ternary Ti–Mo–Al alloys, two-stage yielding was found in the tensile examinations. Among all the alloys, the Ti–5.5Mo–4Al, the Ti–5.5Mo–4Al–6Zr, and the Ti–5.5Mo–8Al–6Zr (mol pct) alloys performed excellent shape recovery of about 100 pct in the bending and heating tests. Especially, the Ti–5.5Mo–4Al–6Zr and the Ti–5.5Mo–8Al–6Zr alloys further show high strength. Results in this study could be a guideline for the design of the fundamental Ti–Mo–Al-based SMAs.

Impact behavior of spark plasma sintered Ti–Al–Mo/TiN composites: a finite element analysis approach using Abaqus CAE

BackgroundThe utilization of Finite Element Analysis (FEA) has emerged as a crucial methodology in the field of structural and elasticity analysis, facilitating researchers in their understanding of material responses to diverse thermal or structural loads. This study investigates the utilization of FEA to simulate the Impact characteristics of titanium composites, with specific emphasis on the Charpy impact test. The research utilizes the Abaqus Explicit software, which is widely recognized for its explicit dynamic analysis functionalities, to simulate high-speed and short-duration events such as impacts. The primary objective of this study is to examine the impact behavior of Ti–7Al–1mo/TiN composites fabricated through the spark plasma sintering technique. The impact behavior is simulated using FEA, wherein the shear failure model is utilized to replicate fracture phenomena. This paper examines the methodology employed in the FEA approach, with a particular focus on various factors including boundary conditions, explicit dynamic analysis settings, and material properties.ResultsThe outcomes and analyses involve the examination of the von Mises stress distribution, displacement magnitude, and energy behavior of the models that were tested. Reinforcement of Ti–Al–Mo ternary alloy with TiN led to a progressive increase in maximum von Mises stress, reaching a peak at 3 wt% TiN. Conversely, displacement magnitude decreased with increasing TiN content, with CP-Ti and the unreinforced alloy exhibiting the highest values. Absorbed energy also declined with higher TiN levels. While models containing 5 and 7 wt% TiN displayed limited plastic deformation before fracture, composites with ≤ 3 wt% TiN maintained acceptable ductility despite enhanced strength and stiffness.ConclusionThe FEA methodology effectively simulates the Charpy impact characteristics of Ti–7Al–1Mo/TiN composites, thereby offering significant contributions to understanding their mechanical behaviors. These findings suggest that TiN reinforcement up to 3 wt% presents a promising strategy for improving the mechanical performance of Ti–Al–Mo alloys while minimizing the trade-off in toughness. This research emphasizes the inherent trade-off between toughness and strength/stiffness, suggesting the possibility of optimizing the composition of materials to suit particular applications. This study makes a valuable contribution to the expanding field of impact behavior research, demonstrating the potential of FEA, specifically utilizing Abaqus Explicit software, for enhancing material design and evaluation.

Corrosion resistance investigation of the Ti–Al–Mo system supported by CALPHAD approach and key experiments

The corrosion resistance of Ti–Al–Mo alloys in seawater were investigated by thermodynamic calculations and electrochemical tests. Four as-cast alloys were designed based on thermodynamic calculations. The calculated results were verified by experimental determination. The Gibbs energy and electrochemical experiment results showed Ti55Al40Mo5 alloy has the most positive Gibbs energy and the best corrosion resistance. The bcc(Ti) phase has best corrosion resistance among AlTi, AlTi3 and bcc(Ti). The present work further proves the important role of phase diagram calculation in alloy design, and thermodynamic database provides important theoretical support for efficient development of new alloys.

Development and Characterization of Al-15%Mo Binary Alloys

In this work, a binary Al-Mo alloy was made from aluminum and molybdenum elementary powder. The carefully homogenized samples were mechanically compacted to obtain a pastille of circular cross section (Φ=15 mm X 10 mm) under a load of 10 tons. Subsequently, the Al-Mo sample was melted in a high-frequency induction melting furnace. The resulting sample was polished and etched with a Keller reagent.The sample was subjected to metallographic observation on an optical and scanning electron microscope. An EDS analysis was performed on the different areas of the microstructure. A diffraction X-ray characterization was also performed in order to identify the different existing phases. This study showed that the studied alloy presents a microstructure with needle-like and plate-like precipitations of different sizes homogeneously distributed and randomly oriented. The EDS microanalysis showed the presence of the Al-5Mo phase and an alpha aluminum matrix with a proportion of molybdenum. X-ray diffraction revealed the presence of several AL-Mo phases’ namely alpha aluminum, molybdenum, Al12Mo, Al8Mo3 and Al3Mo.

Al Electrodeposition in Molten CaCl2 with Various Calcium Aluminates

An innovative production process of Al metal is desired to reduce CO2 and perfluorocarbon gas generation. Our previous study showed that calcium titanate and silicate dissolved in molten CaCl2. Ti and Si metals could be electrodeposited, and it was indicated that Ti and Si reductions depended on the molar ratio of CaO to TiO2 or SiO2. In this study, direct production of liquid Al metal was attempted in molten CaCl2 with various calcium aluminates.Molten CaCl2 at 1373 ~ 1573K in an Ar atmosphere was used as a bath. Calcium aluminate (molar ratio of CaO to Al2O3, RCaO/Al2O3 =1.0, 12/7 or 3.0) was prepared by sintering a molded mixture of CaO and Al2O3, and it was added in CaCl2 beforehand. Mo and graphite rods were used a working and counter electrode, respectively. Mo wire was used as a quasi-reference electrode. The cathodic reaction was investigated by cyclic voltammetry, and potentio-static electrolysis was carried out. The electrodeposit was analyzed by XRD and SEM-EDX.Although no sharp current peak was seen, cathode current increased overall with calcium aluminate addition. The shape of CVs slightly changed with RCaO/Al2O3, but RCaO/Al2O3 seemed not to affect Al reduction significantly.Al and Al-Mo alloy were detected in the electrode after the electrolysis at -1.8V at 1573K regardless of RCaO/Al2O3, but the Al amount was very small. So, a Mo cathode with BN receiver in the bottom shown Fig.1 was used to prevent deposited Al metal from running down from the cathode. Al metal covered the surface by electrolysis, and a thick Al-Mo alloy layer was found in its cross section. It was shown that calcium aluminate dissolved in molten CaCl2 above 1573K, and that Al metal could be deposited electrochemically. The molar ratio of CaO to Al2O3 slightly affected the Al deposition though its influence have not clarified well.

Al Electrodeposition in Molten CaCl2 with Various Calcium Aluminates

In this study, direct production of liquid Al metal was attempted in molten CaCl2 with various calcium aluminates, based on our previous studies on Ti and Si electrolysis. Al and Al-Mo alloys were detected on the electrode surface after electrolysis at -1.8V (Mo vs. dissolution) at 1573K, and the molar ratio of CaO to Al2O3 did not affect Al deposited strongly. By using the electrode with a BN receiver, the electrodeposited Al was kept around the cathode and Al was obtained from the cathode surface. It was shown that calcium aluminate was dissolved in molten CaCl2 above 1573 K and liquid Al metal could be obtained electrochemically with little dependence on the molar ratio of CaO to Al2O3.

Hot-injection for synthesizing ammonium thiosulfate precursor of molybdenum disulfide thin film coated on nano-porous aluminum oxide for surface strengthening

A cheap and massive producible ammonium thiosulfate precursor has been synthesized by hot-injection method for coating MoS2 layer onto the nano-porous anodic aluminum oxide (AAO) layer on the surface of 7003 alloy. The ammonium thiosulfate precursor is pyrolyzed at 280, 375, 400 and 550 °C to form the MoS2 layer, respectively. After 1440 m wear test, the wear rates (weight loss/original weight) of pure 7003 alloy, anodized 7003 alloy and MoS2 coated 7003 alloy pyrolyzed at 400 °C are 0.339%, 0.017%, and 0.0109%, respectively. The thickness of the molybdenum disulfide film observed by transmission electron microscope is about 43.3 nm. The surface hardness of MoS2 coated 7003 alloy is about 5–6 GPa higher than that of AAO, 3–4 GPa measured by nanoindentation. The maximum reduced modulus of elasticity is about 90 GPa as the pyrolytic temperature reaches 400 °C. The ratio of the average surface hardness (H∗) and reduced modulus of elasticity (E∗) is linearly proportional to the elastic recovery rates (We), calculated from the maximum indentation depths with different pyrolytic temperatures. The elastic recovery rate would remain in a range of the pyrolytic temperatures between the occurrence of solid solutionization and completion of the solid solution homogenization for Al–Mo alloy formation.

Dual-phase synergetic precipitation in Nb/Ta/Zr co-modified Fe–Cr–Al–Mo alloy

The present work investigated the synergetic effect of Nb/Ta/Zr co-alloying on the microstructural stability of precipitates in the body-centered-cubic (BCC) matrix at high temperatures in Fe-13.5Cr-4.7Al-2.1Mo-0.5Nb-0.8Ta-0.2Zr (wt. %). Alloy plates were fabricated by vacuum arc melting and multi-pass hot rolling, then aged at 1073 K for 24 h, and finally re-treated at different temperatures (1273–1473 K) for 1 h to study the re-dissolution of precipitates. A large amount of Fe2M (M = Mo,Nb,Zr,Ta) Laves phase particles with a high-entropy effect were dispersed on BCC matrix with a volume fraction of f ~ 4.6% in 1073 K-aged alloy. These particles were then coarsened and dissolved into matrix obviously after high temperatures re-treatments, as evidenced by the amount of particles with f ~ 0.7% at 1473 K. More importantly, this value is about ten times higher than that in alloys without Zr addition (f ~ 0.05%), in which these particles are still distributed both in inner grains and on grain boundaries. The higher microstructural stability at high temperatures is ascribed to the co-precipitation of Fe2M, Fe23Zr6, and core(Fe23Zr6)-shell(Fe2M)-structured particles, rather than Laves phase alone. The mechanical property of this alloy at both room and high temperatures was also studied.

Influence of Mo concentration on the structure, mechanical and thermodynamic properties of Mo–Al compounds from first-principles calculations

The refractory metal Mo–Al compounds are potential high-temperature materials because of the high melting-point and excellent mechanical properties. However, the structure and related overall performances of Mo–Al alloys are unclear. Here, we apply the first-principles approach to study the influence of Mo concentration on the structure, elastic and thermodynamic properties of Mo–Al compounds. The results show that five phases: cubic MoAl12, rhombohedral MoAl5, monoclinic MoAl4, monoclinic Mo3Al8 and cubic Mo3Al are thermodynamic and dynamical stability. One novel tetragonal Mo2Al(I4/mmm) is predicted. The convex hull shows that Mo3Al8 is more thermodynamically stable than that of the other Mo–Al alloys. Moreover, the bulk modulus of Mo–Al alloys increase gradually with increasing Mo concentration. The bulk modulus, shear modulus and Young's modulus of Mo3Al are 220.7 GPa, 123.5 GPa and 312.3 GPa, respectively, which are larger than the other Mo–Al alloys. The high elastic properties are that the high concentration of Mo forms the numerous Mo–Al bonds due to the interaction between Mo and Al. The calculated Debye temperature of Mo–Al alloys obeys the sequence of Mo3Al8>MoAl4>MoAl5>MoAl12>Mo3Al > Mo2Al. The phonon density of state demonstrates that the high-temperature thermodynamic properties of Mo–Al alloys are determined by the vibration of Al atom and Mo–Al bond.

High-temperature mechanical behavior of B2-ordered Ti–Mo–Al alloys

Compressive stress–strain responses of stoichiometric and off-stoichiometric B2-ordered Ti–Mo–Al alloys over the temperature range 973–1373 K were examined to investigate the effects of composition and temperature on the mechanical behavior. The Ti–Mo–Al alloys exhibited impressive yield strengths at elevated temperatures, e.g., 818 MPa for Ti50Mo35Al15 at 1073 K and 490 MPa for Ti50Mo25Al25 at 1273 K. Positive temperature dependence of yield strength was observed in Ti50Mo25Al25 below 1273 K but it had not been seen in either Ti60Mo25Al15 or Ti50Mo35Al15 throughout the test temperatures. Dislocation analyses of the compressed specimens indicated that the Ti–Mo–Al alloys primarily deformed via <111>slip. The mechanisms responsible for the variations of mechanical properties with composition and temperature are discussed by correlating with the antisite defects.

Excess aluminium effect on the composition and microstructure of Mo–Al alloys from aluminothermic reduction of MoO3

ABSTRACTThe effect of aluminium excess on the composition and microstructure of Mo–Al alloys from aluminothermic reduction of metallurgical-grade MoO3 was investigated. Aluminium excess ranged from 0 to 30% (in wt-%) with respect to the stoichiometric amount. The results showed that molybdenum yield increases for higher excess aluminium. The microstructure and composition of the alloys were investigated using scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and X-ray diffraction (XRD). The following phases were observed in the microstructures: Moss, Mo3Al, and Mo3Al8, besides particles of Al2O3. The results also showed that metallurgical-grade MoO3 leads to a product containing significant amounts of silicon.

High-throughput measurements of interdiffusivity matrices in face centered cubic Ni–Al–Mo alloys at 1273–1473 K

Abstract

New Aluminum Base Materials for Use on Electrical Purposes

Modern power industry expects new, dedicated aluminum based alloys with non-standard properties, including increased resistance to temperature. Materials exhibiting higher thermal resistance allow to increase operating temperature of electrical conductors, which results in the increase of their current carrying capacity. Commonly known and used in such applications are alloys from the AlZr group. Despite their advantages scientists from around the world are searching for new alternatives. In this paper authors present research results on Al-Mo and Al-Ag alloys with particular interest to the analysis of the molybdenum addition to the aluminum in the amount of 0.05, 0.1, 0.2% and silver addition in the amount of 0.05, 0.1, 0.15% by mass on the mechanical and electrical properties of obtained alloys. Tests were also carried out for reference material which is high-purity aluminum and the AlZr alloy, both in the as cast state temper. Results showed a significant change of temperature coefficient of resistance in Al-Ag alloys compared to Al, which leads to possible increase of the Joule’a heat without the raise of conductors temperature limit. On the other hand, above-average heat resistance of alloys from the Al-Mo group of materials was achieved during the trials. On that basis authors state that Al-Ag alloys may be used for the production of ACSS conductors and Al-Mo alloys for TACSR or TACIR type of conductors.This study was performed under a project financed by NCBiR within the INNOTECH II program.

A new class of high strength high temperature Cobalt based γ–γ′ Co–Mo–Al alloys stabilized with Ta addition

The present paper reports a new class of Co based superalloys that has γ–γ′ microstructure and exhibits much lower density compared to other commercially available Co superalloys including Co–Al–W based alloys. The basic composition is Co–10Al–5Mo (at%) with addition of 2at% Ta for stabilization of γ′ phase. The γ–γ′ microstructure evolves through solutionising and aging treatment. Using first principles calculations, we observe that Ta plays a crucial role in stabilizing γ′ phase. By addition of Ta in the basic stoichiometric composition Co3(Al, Mo), the enthalpy of formation (ΔHf) of L12 structure (γ′ phase) becomes more negative in comparison to DO19 structure. The ΔHf of the L12 structure becomes further more negative by the occupancy of Ni and Ti atoms in the lattice suggesting an increase in the stability of the γ′ precipitates. Among large number of alloys studied experimentally, the paper presents results of detailed investigations on Co–10Al–5Mo–2Ta, Co–30Ni–10Al–5Mo–2Ta and Co–30Ni–10Al–5Mo–2Ta–2Ti. To evaluate the role alloying elements, atom probe tomography investigations were carried out to obtain partition coefficients for the constituent elements. The results show strong partitioning of Ni, Al, Ta and Ti in ordered γ′ precipitates.

Thermal stability of Al–Mo thin film alloys

Thin AlxMo100−x films (40 ≤ x ≤ 90 with x in steps of 5 at % Al) were prepared by magnetron co-deposition onto alumina, glass, and saphire substrates at room temperature. The film thickness was about 400 nm, and they were amorphous for 45 ≤ x ≤ 85. The films' structural changes upon heating were investigated by measurement of the electrical resistivity variation with temperature, ρ(T), during the isochronal heating. Thus obtained results were complemented, and conclusions confirmed, by GIXRD analysis for selected heating temperatures. The dynamical temperatures of crystallization, Tx, were determined from the sharp increase of the derivative of ρ with respect to temperature. No systematic dependence of Tx on film substrate has been observed. Except for the Al85Mo15 film, the ρ of the amorphous films increase on the crystallization. The temperature of crystallization exhibits maximum around 530 °C for alloy compositions with x = 55 and 60. Electrical resistivity of both amorphous and crystallized films show a strong dependence on alloy composition, with a maximum for Al75Mo25 alloy. The resistivity of Al75Mo25 film is very large and amounts to 1000 μΩ cm and 3000 μΩ cm in amorphous and crystallized film, respectively, with the large negative temperature coefficient of −10 × 10−4 K−1 and −14×10−4K−1, respectively. Although the crystallization temperature observed for the examined amorphous Al–Mo alloys is not very high, it might allow to exploit excellent corrosion properties of such films at some elevated temperatures.

Oxidation Characteristics of Thin Al–Mo Alloy Films with Various Compositions as Metal Capping Layer on Cu

The oxidation characteristics of Al–Mo alloy films (50 nm) deposited on Cu as a metal capping layer have been examined by varying the alloy composition. Cu oxidation from the surface and Cu out-diffusion toward the surface are well suppressed when using Al–Mo alloy with a Mo-rich composition. By using an Al15Mo85 alloy film, in which fine crystalline grains of AlMo3 are dispersed in an amorphous phase of the alloy, a well-separated layer configuration of oxide/Al–Mo alloy/Cu without excess Cu diffusion and/or preferential Al oxidation in the alloy layer is realized upon oxidation at 350 °C for 1 h in air. It is revealed that Al15Mo85 alloy films are a useful candidate material of a metal capping layer for Cu interconnects.

Oxidation Characteristics of Thin Al–Mo Alloy Films with Various Compositions as Metal Capping Layer on Cu

The oxidation characteristics of Al–Mo alloy films (50 nm) deposited on Cu as a metal capping layer have been examined by varying the alloy composition. Cu oxidation from the surface and Cu out-diffusion toward the surface are well suppressed when using Al–Mo alloy with a Mo-rich composition. By using an Al15Mo85 alloy film, in which fine crystalline grains of AlMo3 are dispersed in an amorphous phase of the alloy, a well-separated layer configuration of oxide/Al–Mo alloy/Cu without excess Cu diffusion and/or preferential Al oxidation in the alloy layer is realized upon oxidation at 350 °C for 1 h in air. It is revealed that Al15Mo85 alloy films are a useful candidate material of a metal capping layer for Cu interconnects.

Phase transition and ordering behavior of ternary Ti–Al–Mo alloys using in-situ neutron diffraction

Abstract Neutron diffraction has been used for in-situ investigations to elucidate the phase transformation behavior of two Mo-containing TiAl alloys with compositions of Ti-44Al-3Mo and Ti-44Al-7Mo (in at.%). Five different phases are present in these alloys. These include three ordered phases at room temperature, namely α2, β0 and γ and two disordered phases, and, which occur at higher temperatures. The sequence of the three phase transformations in each alloy has been determined. The phase transformation and disordering/ordering temperatures were determined on heating and cooling from the diffracted peak intensities. The neutron experiments are particularly sensitive to the order–disorder transitions in TiAl alloys, which are compared with the overall phase fractions obtained from previous high energy X-ray diffraction. Hysteresis and undercooling effects are observed for the various phase transformations and depend on the nature of atomic rearrangements.

ChemInform Abstract: Passive Film Structure of Supersaturated Al-Mo Alloys.

Reflection-extended x-ray absorption fine-structure spectroscopy has been used to probe the local atomic structure of the passive film of supersaturated A1-Mo alloys polarized in KC1. These alloys (with 7-11 atom percent Mo) exhibit resistance to localized attack with an increase in the pitting potential of -600 mV relative to pure aluminum. Measurements show that the structure of the A1-Mo passive films resembles that of a-A12OjA1OOH, whereas an oxide film grown on pure A1 in tartaric acid, which does not possess enhanced passivity, is more like ~-A12OJA1OOH. Complementary x-ray photoelectron spectroscopy measurements indicate the A1-Mo passive film composition to be near that of A1OOH and the tartaric-acid film to be A1203. Because corundum (a-A1203) and diaspore (a-A1OOH), which contain only octahedrally coordinated A1 atoms, are very stable and inert while ~/-A1203, which contains both octahedral and tetrahedral sites, is reactive, the change in structure of the passive film suggests that improved passivity may be correlated with a reduction in the density of tetrahedrally coordinated atoms. This structural change likely results from the incorporation of oxidized Mo into the passive film; only as this Mo is hydrated with a presumed change in local structure does the alloy pit. Aluminum and conventional aluminum alloys are susceptible to localized attack in chloride-containing environments. Although passivity-promoting alloying species,

Passivation of Aluminum–Molybdenum Alloys in Hydrochloric Acid

The electrochemical properties of the system Al–Mo alloy∣anodic oxide film∣1.0 M HCl solution were investigated as a function of alloy composition and applied potential in 1.0 M HCl. Voltammetry measurements have revealed that the alloy systems with behave almost like pure Mo. The alloy systems with showed the potential regions of primary and secondary passivities in which the structural and protective properties of the anodic oxide films were studied using electrochemical impedance spectroscopy. Orazem’s graphical methods and Mott–Schottky analysis were used to extract the values of parameters of the constant-phase element, interfacial capacitance, ohmic resistance, type of conductivity, and concentration of charge carriers in the semiconducting oxide film, which are all from the high frequency impedance data. The pseudoinductive behavior observed at low frequencies in the potential range of the secondary passivity was discussed in terms of the surface-charge approach based on the chemistry of the point defect model.