Cast Titanium Alloys Research Articles

Research on the Impact Behavior of Molten Metal on the Mold Shell in Gravity Casting of Large Titanium alloy Castings

The impact behavior of molten metal on the mold shell in gravity casting of large titanium alloy castings by investment precision castings was studied. The physical and mechanical models of the impact of molten metal on the mold shell during the pouring process were constructed using numerical simulation. The effects of molten metal pouring rate and pouring weight on the maximum impact force of the mold shell were studied. The research results indicated that during the entire pouring process, the impact force of the first molten metal contacting the mold shell was higher than subsequent molten metal. The maximum impact force increased with the increase of pouring rate and pouring weight. The total impact force of the molten metal on the mold shell was composed of the instantaneous impact force converted from instantaneous impulse and itself gravity. The instantaneous impact force of the molten metal that first impacts the mold shell was much greater than its own gravity, while the impact force of the molten metal at the end of pouring was much less than its own gravity. The maximum impact force on the mold shell of a large casting with a pouring weight of 800kg was about three times higher than that of a medium-sized casting with a pouring weight of 80kg.The difference in the total impact force on the mold shell between them mainly comes from the instantaneous impact force converted from instantaneous impulse.

Investigation into relationships between grain size distribution characteristics and mechanical properties in large-scaled complex titanium alloy castings utilizing LASSO regression

Investigation into relationships between grain size distribution characteristics and mechanical properties in large-scaled complex titanium alloy castings utilizing LASSO regression

Evolution of microstructure and mechanical properties in large-scaled complex titanium alloy castings during service based on quantitative abnormal microstructure analysis

This investigation delves into the microstructural heterogeneities of large-scale complex titanium alloy castings (LCTACs), with a specific focus on the emergence of abnormal coarse grains (ACGs), which pose a potential threat to the casting's operational longevity. This comprehensive analysis meticulously maps the spatial distribution of ACGs within the LCTAC, employing statistical methodologies to examine these grains across different zones subjected to varying service durations. The study reveals a nuanced correlation between wall thickness and the tendency for microstructural coarsening during operational life, concurrently tracing the evolution of mechanical properties in typical zones. Results demonstrate a distinctive 'staircase-like' progression in grain size distribution, accentuated as wall thickness increases. Throughout the operational lifespan, microstructures in zones of differential wall thickness exhibit varied degrees of growth. Notably, zones with thicker walls display a more marked enlargement in microstructure. This phenomenon coincides with a substantial increase in the extent of ACGs, ultimately leading to a significant diminution in mechanical properties, evidenced by a reduction exceeding 15% in both tensile and yield strength.

Electrochemical anodization of cast titanium alloys in oxalic acid for biomedical applications

Titanium and its alloys have numerous biomedical applications thanks to the composition and morphology of their oxide film. In this study, the colorful oxide films were formed by anodizing cast Ti-6Al-4V and Ti-6Al-7Nb alloys in a 10% oxalic acid solution for 30 s at different voltages (20–80 V) of a direct current power supply. Atomic force microscopy was used as an accurate tool to measure the surface roughness of thin films on the nanometer scale. Scanning electron microscopy and X-ray diffraction were performed to analyze surface morphology and phase structure. According to the results, the produced titanium oxide layer showed high surface roughness, which increased with increasing anodizing voltage. The impact of anodizing voltages on the color and roughness of anodized layers was surveyed. The corrosion resistance of the anodized samples was studied in simulated body fluid at pH 7.4 and a temperature of 37 °C utilizing electrochemical impedance spectroscopy and the potentiodynamic polarization method. The anodized samples for both alloys at 40 V were at the optimal voltage, leading to a TiO2 layer formation with the best compromise between oxide thickness and corrosion resistance. Also, findings showed that TiO2 films produced on Ti-6Al-7Nb alloys had superior surface roughness properties compared to those of Ti-6Al-4V alloys, making them more appropriate for orthopedic applications. From the obtained data and the fruitful discussion, it was found that the utilized procedure is simple, low-cost, and repeatable. Therefore, anodization in 10% oxalic acid proved a viable alternative for the surface finishing of titanium alloys for biomedical applications.

Preparation of yttrium oxide coating with enhanced thermal shock resistance on refractories used for titanium alloy melting and casting

Preparation of yttrium oxide coating with enhanced thermal shock resistance on refractories used for titanium alloy melting and casting

Effect of Structural Features on Microstructure and Properties Homogeneity Based on Quantification and Statistical Analysis for Large-Scaled Complex Titanium Alloy Castings

Effect of Structural Features on Microstructure and Properties Homogeneity Based on Quantification and Statistical Analysis for Large-Scaled Complex Titanium Alloy Castings

Effect of CaTiO3 on sintering properties of Y2O3 -based ceramic shell via extrusion-based 3D printing for titanium alloy casting

Yttrium oxide (Y2O3) is widely used in titanium (Ti) alloy casting for its low activity, strength, and heat resistance. Wax mold and ceramic coating preparation in traditional investment casting is cumbersome; hence, this work proposes extrusion-based 3D printing of Y2O3-based ceramic shells. This study investigates how trace CaTiO3 affects sintering performance, showing that small amounts can reduce sintering temperature and significantly increase bending strength. Adding 2 mol% CaTiO3 increased the bending strength from 4.3 to 43.1 MPa after sintering at 1500 °C, while not wetting with the Ti–6Al–4V titanium alloy. This method offers a promising way to produce high-performance Y2O3-based ceramic shells with lower sintering temperatures.

Effect of multi-purpose primer on bonding of acrylic resin to cast titanium and gold alloy after airborne-particle abrasion.

To clarify the effect of a multi-purpose primer combining several functional monomers on two prosthodontic materials (cast titanium and a gold alloy) after airborne-particle abrasion. Disk-shaped adherends were prepared from cast titanium (CP Titanium JIS2) and a gold alloy (Casting Gold M.C. Type IV). A silane-containing two-liquid primer (M&C primer (MC)) and two silane-free single-liquid primers (Alloy Primer (AP) and V-Primer (VP)) were used as surface-treatment agents. The shear bond strengths were determined before and after thermocycling to evaluate the adhesive durability, and the results were compared using a non-parametric statistical analysis. The effect of airborne-particle abrasion with alumina on the titanium surface was analyzed by X-ray photoelectron spectroscopy (XPS). There was no significant difference in bond strength between the MC and AP before and after thermocycling, whereas VP showed significantly lower values. XPS revealed that the titanium acquired hydrophilic properties after the airborne-particle abrasion. The novelty of this study is that it shows that the presence/absence of the silane had no effect on the bonding of cast titanium with an acrylic resin. The study also showed that the multi-purpose primer can be used without any problems with both cast titanium and gold alloy, in combination with airborne-particle abrasion with alumina.

Effect of hot isostatic pressing processing parameters on microstructure and properties of Ti60 high temperature titanium alloy

Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in aerospace. In order to obtain optimal processing parameters, the effects of hot isostatic pressing parameters on defects, composition uniformity, microstructure and mechanical properties of Ti60 cast high temperature titanium alloy were investigated in detail. Results show that increasing temperature and pressure of hot isostatic pressing can reduce defects, especially, the internal defects are substantially eliminated when the temperature exceeds 920 °C or the pressure exceeds 125 MPa. The higher temperature and pressure can improve the microstructure uniformity. Besides, the higher pressure can promote the composition uniformity. With the temperature increases from 880 °C to 960 °C, α-laths are coarsened. But with increasing pressure, the grain size of prior-β phase, the widths of α-laths and α-colony are reduced. The tensile strength of Ti60 alloy is 949 MPa, yield strength is 827 MPa, and the elongation is 11% when the hot isostatic pressing parameters are 960 °C/125 MPa/2 h, which exhibits the best match between the strength and plasticity.

New Technological Solutions in the Manufacture of Thermochemically Resistant Ceramic Molds for Casting Titanium Alloys

New Technological Solutions in the Manufacture of Thermochemically Resistant Ceramic Molds for Casting Titanium Alloys

New process solutions in the manufacture of thermochemically resistant ceramic molds for casting titanium alloys

The paper provides the results of studies on interaction between titanium melts and silica-containing investment molds. Pure silicon, compounds of titanium oxides and silicides were detected by X-ray diffraction analysis in the contact zone. The problem of the negative impact exerted by the mold on the casting is solved by using thermally stable and chemically resistant monocorundum molds based on an alumina sol binder. A refractory suspension was developed for investment casting containing special additives to improve wax mold wetting with the suspension, and to increase the mold shell strength. The article studies sedimentation properties of suspension. A method was developed for accelerated curing of sequentially applied refractory suspension layers by vacuum drying and subsequent chemical curing with a gaseous reagent. The formation time is reduced from 3–5 h to 20–30 min per layer. Comparative studies of kinetics of alumina sol binder convective drying and vacuum dehydration were conducted. The process of moisture removal per unit surface of the applied refractory layer in a vacuum of 5–10 kPa increases by 2–6 times. X-ray phase analysis was used to study the alumina sol conversion during high-temperature heating. The solid gel of the α-Al2O3 stable phase is obtained in the alumina sol mold shell when the calcination temperature rises to 1300–1350 °C with a sufficient strength of 9–12 MPa provided by sintering additives added to the suspension. Recommendations are given for additional protection of refractory ceramic layers after vacuuming and drying: treatment of the last layer with gaseous curing agents and application of a polyvinylacetal solution with a density of 1100–1200 kg/m3. The process solutions proposed will make it possible to increase both the efficiency of titanium alloy forming and casting processes and the quality of castings.

Improvement of mechanical properties and microstructural refining of cast titanium alloys by coupling of electropulsing and temporary alloying element hydrogen

The electric pulse treatment and hydrogen as temporary alloying element have been widely used to improve the microstructure and mechanical properties of titanium alloys, respectively. In this study, the microstructure and mechanical properties of as-cast Ti–6Al–4V alloy are improved by electric pulse treatment combined with temporary alloying element hydrogen instead of traditional thermo-mechanical treatment and heat treatment. In comparison to the traditional thermo-mechanical treatment, the microstructure of the as-cast Ti–6Al–4V alloy after solution-aging treatment in pulsed thermal hydrogen treatment is homogeneous and finer, which is due to the lamellar β phase decomposition after thermal hydrogen treatment, accordingly, the ultimate tensile strength and total elongation of the alloy are effectively improved after pulsed thermal hydrogen treatment. It’s the acceleration of atomic diffusion and phase transformation in titanium alloys by hydrogen as temporary alloying element and electric pulse treatment that leads to the decomposition of the lamellar β phase, thereby refining the microstructure and enhancing mechanical properties. Finally, a novel method for improving the microstructure and mechanical properties of titanium alloys using hydrogen as temporary alloying element and electric pulse treatment is presented.

Ceramic molds based on yttrium oxide for the casting of titanium alloys

The effect of various binding agents based on aqueous solutions of nitric acid, yttrium nitrate and orthophosphoric acid and yttrium hydroxide gel on the physical and mechanical properties of casting molds based on Y2O3 has been studied. It is shown that the most promising binding agent for yttrium oxide casting molds is a phosphate bond. The data describing the curing mechanism of phosphate-bonded molding mass is presented. The influence of the concentration of binding agent solutions on the strength characteristics of molding materials after curing and heat treatment is shown. Information about the interaction of yttrium oxide powder molds with phosphate-binding with titanium melt of VT1-0 and VT6 grades is presented. The obtained data allowed us to describe the advantages and disadvantages of the developed molding compound. A method for producing casting molds based on yttrium oxide powder with a yttrium phosphate-binding agent was developed based on this research.

Multi-stage hot deformation and dynamic recrystallization behavior of low-cost Ti–Al–V–Fe alloy via electron beam cold hearth melting

To explore the optimal thermomechanical processing parameters (TMP) of Ti–Al–V–Fe alloys with direct rolling potential after electron beam cold hearth melting (EBCHM) and the grain refinement mechanism during thermal deformation, the multi-pass hot deformation and dynamic recrystallization (DRX) behavior of Ti–4Al–2.5V–1.5Fe alloy ingot produced via EBCHM were investigated in this paper. The multi-pass compression tests were conducted on a Gleeble-3500 thermal simulation experimental machine with deformation temperatures of 850–1000 °C and strain rates of 0.01–1 s−1. The results showed that the flow stress and the microstructure of the alloy were both sensitive to the deformation temperature and strain rate. The as-cast Ti–4Al–2.5V–1.5Fe alloy had the highest fraction of DRX and the smallest average grain size at the deformation temperature of 950 °C and the strain rate of 0.01 s−1 suggest that the DRX mechanism had a significant grain refinement effect. The softening mechanism at higher deformation temperature or lower strain rate was dominated by dynamic recrystallization (DRX). In the continuous dynamic recrystallization (CDRX) mechanism, sub-grain boundaries transformed LAGBs into HAGBs by continuously absorbing dislocations, which was more evident at low deformation temperatures compared to discontinuous dynamic recrystallization (DDRX). In this paper, the original coarse cast titanium alloy grains were refined to smaller sizes through multi-pass thermal deformation, the synergistic regulation laws of thermal deformation behavior and microstructure evolution under different deformation conditions, and the corresponding DRX behavior were elucidated, providing scientific guidance for the direct rolling of cast titanium alloys.

Refining the microstructure to strengthen casting titanium alloy by electric pulse

Thermal-hydrogen treatment can effectively refine the microstructure and improve the thermoforming, machining performance and superplasticity of titanium alloy. In this study, pulsed electric current is used to replace the traditional heat treatment in the thermal-hydrogen treatment of cast titanium alloy, and the experimental results and strengthening effect of pulsed thermal hydrogen treatment and traditional thermal hydrogen treatment were compared. After pulsed thermal-hydrogen treatment, the lamellar β phase is broken into spherical shape and uniformly distributed in the matrix, and the cast titanium alloy was significantly strengthened. However, the microstructure refinement and strengthening effect of traditional thermal-hydrogen treatment is not as good as that of thermal-hydrogen treatment under electric pulse. The process of thermal-hydrogen treatment is accompanied by the formation of new phases, and the nucleation and growth of new phases are often controlled by atomic diffusion. In addition to the necessary thermal effects, the pulsed electric current also provides athermal effects, and thermodynamically lowering the energy barrier and promoting nucleation, while kinetically promoting the diffusion of atoms and accelerating the solid solution process. Therefore, based on the experimental results and analyses, thermal-hydrogen treatment under electric pulses provides a novel and effective method for refining the microstructure to strengthen cast titanium alloys.

Thermodynamic analysis of casting titanium alloys is the basis of information support in the optimal foundry technology development

The necessity of systematic formation of intellectual connections for integration into a single complex of currently fragmented software products for the technological analysis of the castings geometry, thermodynamic modeling of the titanium alloys properties, calculation of molding mixtures thermophysical characteristics for the purpose of conjugate implementation of a set of modeling procedures and casting processes diagnostics of is proved. Lack of such an integrated software package, computer analysis of modeling results in the existing manufacturing products practice demonstrates (by the example of the shrinkage defects distribution in a responsible casting of TL3 alloy) the need for radical technological design tools’ improvement.One of the key components of the “digital technology” being formed in the future is thermodynamic modeling of equilibrium phase transformations, which allows calculating the physico-chemical parameters, thermodynamic, thermophysical and casting parameters of titanium alloys and their evolution in the temperature range of crystallization. Based on thermodynamic simulation, experimental planning apparatus and the experience of statistical analysis carried out, a method for forming models for estimating equilibrium parameters used in modeling foundry processes has been developed, and it shows the possibility of applying it to various casting titanium alloys. For the standard composition of the TL3 alloy, a multifactor system of equations was obtained, reflecting the degree of influence of the components on the fluctuations of the alloy characteristics complex, which determine the development of a series of casting defects. The possibilities of using the obtained models for TL3 alloy and methods of obtaining them for use in computer modeling systems to increase the adequacy and accuracy of the results obtained are described.

In vitro behaviour of human gingival fibroblasts cultured on 3D-printed titanium alloy with hydrogenated TiO2 nanotubes

Selective laser melting (SLM), as one of the most common 3D-printed technologies, can form personalized implants, which after further surface modification can obtain excellent osseointegration. To study the surface properties of SLM titanium alloy (Ti6Al4V) with hydrogenated titanium dioxide (TiO2)nanotubes (TNTs) and its influence on the biological behaviour of human gingival fibroblasts (HGFs), we used SLM to prepare 3D-printed titanium alloy samples (3D-Ti), which were electrochemically anodizing to fabricate 3D-TNTs and then further hydrogenated at high temperature to obtain 3D-H2-TNTs. Polished cast titanium alloy (MP-Ti) was used as the control group. The surface morphology, hydrophilicity and roughness of MP-Ti, 3D-Ti, 3D-TNTs and 3D-H2-TNTs were measured and analysed by scanning electron microscopy (SEM), contact angle metre, surface roughness measuring instrument and atomic force microscope, respectively. HGFs were cultured on the four groups of samples, and the cell morphology was observed by SEM. Fluorescence staining (DAPI) was used to observe the number of adhered cell nuclei, while a cell counting kit (CCK-8) was used to detect the early adhesion and proliferation of HGFs. Fluorescence quantitative real time polymerase chain reaction (RT–qPCR) and enzyme-linked immunosorbent assay (ELISA) were used to detect the expression of adhesion-related genes and fibronectin (FN), respectively. The results of this in vitro comparison study indicated that electrochemical anodic oxidation and high-temperature hydrogenation can form a superhydrophilic micro-nano composite morphology on the surface of SLM titanium alloy, which can promote both the early adhesion and proliferation of human gingival fibroblasts and improve the expression of cell adhesion-related genes and fibronectin.Graphical abstract

Experiment on fluid regime under different rotate velocity in physical simulation of titanium vertical centrifugal casting

In this paper, the physical simulation of filling process of vertical centrifugal casting (VCC) of complex titanium alloy casting was studied. Combined with the mature PTV particle tracking technology, the high-speed photography pictures of the filling process of VCC at different rotational speeds were obtained. The trajectory and velocity information of tracer particles in the rotating flow field were obtained by the corresponding analysis software. Then, through the analysis and modeling of quantitative experimental data, the flow behavior characteristics and movement law of titanium alloy melt in the mold cavity under different mold speeds were studied. The results show that: 1. When the mold is still, the front edge of the filling fluid forms a curved surface with the curvature center pointing to the outside of the mold; when the mold rotates, the front edge of the liquid flow forms a curved surface with the curvature center pointing to the inside of the mold; 2. With the increase of the mold rotation speed, the speed of the fluid filling the mold increases significantly; when the rotational speed is greater than 120 rpm, the fluid still has a certain driving force in the mold center far away from the gate; it is good for filling the inner corner of mold with fluid; and 3. When the rotational speed of centrifugal casting of titanium alloy reaches 45 rpm or above, typical turbulent vortices appear in the wake; with the increase of rotating speed to 180 rpm, the average curvature radius of turbulent vortices first increases and then decreases, and reaches the minimum value of 0.67 cm at 120 rpm.

Mechanical properties of casting titanium alloy matrix composites reinforced by WC and TiB2 ceramic particulates

Casting Titanium alloys with Wc and TiB2 additives have their mechanical characteristics examined in this work. The mechanical properties of aged titanium alloys are very impressive. UTS reach 406 MPa and YS of 253 MPa and an El of 7.4 percent. Pinned primary Wc and TiB2 phases reduced fineness by more than half, while enhancing assorted nucleation on Wc and TiB2 initial phases boosted nucleation and growth resistance. Following the heat treatment, foundational designed with the intent emerged from the substrate. There are no more stages in the shell. Those alloys containing Wc, on the other hand, have cores composed of Wc and TiB2. From 0.1 wt% to 0.2 wt% of Wc and TiB2 content, core radius rises, but shell width does not appear to change, and particle density does not appear to be altered. In time, composite particles became coarser, but their core dimensions stayed nearly same. As predicted, the exponent (n-1) is less than the expected value of 0.33, Perhaps this is because of the low temperature, which prevents a developed a semi state from emerging. The kinetics are consistent with the KV model's predictions.

Improvement of Mechanical Properties and Microstructural Refining of Cast Titanium Alloys by Coupling of Electropulsing and Temporary Alloying Element Hydrogen

Improvement of Mechanical Properties and Microstructural Refining of Cast Titanium Alloys by Coupling of Electropulsing and Temporary Alloying Element Hydrogen