Titanium Zirconium Molybdenum Research Articles

Influence of concentrations of chloride ions on electrochemical corrosion behavior of titanium-zirconium-molybdenum alloy

Abstract Titanium-zirconium-molybdenum (TZM) alloy was fabricated by using powder metallurgy and rolling techniques. Electrochemical corrosion behavior of the alloy was studied quantitatively using potentiodynamic polarization and scanning electron microscope. Effect of different chloride ions concentrations on corrosion resistance and electrochemical corrosion mechanism on TZM alloy was investigated. Results show that pitting corrosion and intergranular corrosion of TZM alloy mainly occurs in sodium chloride solution. Corrosion generates firstly in the form of pitting corrosion around second phase particles and increases with corrosive media Cl − concentration increasing, and then the intergranular corrosion occurs along grain boundaries and defects. Cl − corrosion can effectively destroy the passive film formed on the sample surface. As the Cl − concentration of corrosive media increases, the corrosion rate of TZM alloy increases until 1.0 mol/L and then decreases. TZM alloy exhibits good corrosion resistance when the concentration of Cl − in corrosive media is 0.5 mol/L or 1.5 mol/L.

Investigation on compression behavior of TZM and La2O3 doped TZM Alloys at high temperature

Mechanical properties of Titanium-zirconium-molybdenum (TZM) and La2O3 doped TZM alloys under compression were tested at 1000°C and 1200°C. Microstructure of TZM and La2O3 doped TZM alloys after compressing was characterized by scanning electron microscopy. The effects on La2O3 doping on the high temperature deformation behavior and microstructure evolution of the TZM alloy were analyzed. Results show that La2O3 doping can refine the grain size of TZM alloy. La2O3 doping changes fracture model of TZM alloy. TZM alloy exhibits mainly intergranular fracture, while the La2O3 doped TZM alloy exhibits both intergranular and transgranular fracture mode.

Synthesis of hypoxia-high density TZM alloy based on mechanochemistry and particle size distribution theories

Molybdenum powders were high-energy ball milled for 3, 6, 9 and 12 h respectively, using two ball milling methods: (1) dry milled in vacuum and (2) wet milled in mixed solution of ethanol-polyethylene glycol. The effect of high-energy ball milling on relative density of titanium-zirconium-molybdenum (TZM) alloy was investigated. Particle size distribution and calculated proportion in each size range were designed according to the Dinger-Funk model, reaching the dense packing state. The effects of three different kinds of carbon source (graphite, stearic acid (C18H36O2) and carbon nanotubes (CNTs)) on oxygen content and relative density were analyzed. The effects of carbon source on oxygen content were studied. After high-energy milling, fine molybdenum alloy powder particles and large amounts of dislocations and vacancies are helpful to improve TZM alloy density during solid sintering process. Doping carbon nanotubes (CNTs) into the TZM alloy as carbon source can improve its density and decrease oxygen content, which is more effective than graphite or stearic acid as carbon sources. Higher TZM alloy relative density results in lower oxygen content.

Sliding friction and wear behaviour of Titanium-Zirconium-Molybdenum (TZM) alloy against Al2O3 and Si3N4 balls under several environments and temperatures

Due to its resistant to thermal shock and strength at elevated temperature, Titanium-Zirconium-Molybdenum (TZM) alloy is used for hot-work tooling up to 1500°C. The friction and wear behaviour of the TZM alloy reciprocating against Al2O3 and Si3N4 in different conditions were investigated. It has an adhesion and/or oxidation character with a high coefficient of friction when dry sliding against an alumina ceramic ball. It is characterised with reduced wear in an abrasion mode when reciprocally sliding against a Si3N4 ceramic ball. In addition, the friction and wear between TZM and an Al2O3 ball under unidirectional sliding conditions can be reduced when lubricating molybdenum oxides was formed at higher temperature i.e. 600°C. Finally, the friction and wear mechanisms involved are discussed.

Sintering behavior and mechanical properties of Mo-TZM alloyed with nanotitanium carbide

Molybdenum alloys are used in a number of commercial, defense, nuclear, and aerospace applications that take advantage of their high melting temperature, good creep resistance, and decent mechanical properties at elevated temperature. Titanium-Zirconium-Molybdenum (TZM) alloys are the most commercially important Mo alloy as they possess substantially higher strength than pure molybdenum while still maintaining strong mechanical performance at elevated temperature. High density components of these alloys are of interest for high performance defense and aerospace applications, however obtaining high relative densities by sintering has proven difficult. Here we report nano-titanium carbide addition as an effective method of improving TZM sintered density as well as increasing alloy hardness and flexural strength. Pure TZM was sintered by Field Assisted sintering Technique (FAST) to over 98.5% density at 2000°C under 55MPa applied pressure, while density was improved to >99% using TiC addition. TiC addition was found to result in reduced grain size and improved hardness of as-sintered alloys, including over a 95% reduction in grain size and 75% increase in hardness for TZM with 10vol%TiC addition.

Oxidation resistance of Si-coated TZM alloy prepared through combined process of plasma spray and laser surface melting

Plasma thermal spraying of Si coating layer on titanium–zirconium–molybdenum (Ti–Zr–Mo), TZM alloy, was conducted for the surface protection of the Mo substrate that is unstable in air at high temperatures. Although the plasma thermal spraying alone could protect the Mo alloy from oxidation at a high temperature for a short time, the post laser surface melting process further improved the oxidation resistance of Si-coated alloy. In the case of the post laser treated specimen, MoSi compounds, mainly MoSi2 phases, were formed during the additional annealing process, and the oxidation resistance could be even further enhanced. The corrosion behaviors of Si-coated specimens in 3.5% NaCl solution were also investigated; however, no significant variations with respect to the post treatment procedure were found.

Conceptual design of a pre-loaded liquid lithium divertor target for NSTX-U

In this work, a conceptual design for a pre-filled liquid lithium divertor target for the National Spherical Torus Experiment Upgrade (NSTX-U) is presented. The design is aimed at facilitating experiments with high lithium flux from the plasma facing components (PFCs) in NSTX-U and investigating the potential of capillary based liquid lithium components. In the design, lithium is supplied from a reservoir in the PFC to the plasma facing surface via capillary action in a wicking structure. This working principle is also demonstrated experimentally. Next, a titanium zirconium molybdenum (TZM) prototype design is presented, required to withstand a steady state heat flux peaking at 10MWm−2 for 5s and edge localized modes depositing (130kJ in 2ms at 10Hz). The main challenge is to sufficiently reduce the thermal stresses. This is achieved by dividing the surface into brushes and filling the slots in between with liquid lithium. The principle of using this liquid “interlayer” allows for thermal expansion and simultaneously heat conduction, and could be used to significantly reduce the demands to solids in future PFCs. Lithium flow to the surface is analyzed using a novel analytical model, ideally suited for design purposes. Thermal stresses in the PFC are analyzed using the finite element method. The requirements are met, and thus a prototype will be manufactured for physical testing.

Acidic ammonothermal growth of gallium nitride in a liner-free molybdenum alloy autoclave

This paper discusses promising materials for use as internal, non-load bearing components as well as molybdenum-based alloys for autoclave structural components for an ammonothermal autoclave. An autoclave was constructed from the commercial titanium–zirconium–molybdenum (TZM) alloy and was found to be chemically inert and mechanically stable under acidic ammonothermal conditions. Preliminary seeded growth of GaN was demonstrated with negligible incorporation of transition metals (including molybdenum) into the grown material (<1017cm−3). Molybdenum and TZM were exposed to a basic ammonothermal environment, leading to slight degradation through formation of molybdenum nitride powders on their surface at elevated temperatures (T>560°C). The possibility of a ‘universal’, inexpensive, liner-free ammonothermal autoclave capable of exposure to basic and acidic chemistry is demonstrated.

Effect of Laser Surface Treatment on the Corrosion Behavior of FeCrAl-Coated TZM Alloy

The current study involves the coating of Titanium-Zirconium-Molybdenum (TZM) alloy with FeCrAl through plasma thermal spraying which proved effective in improving the oxidation resistance of the substrate. A post-laser surface melting treatment further enhanced the surface protection of the TZM alloy. Oxidation tests conducted at 1100 °C in air indicated that some Mo oxides were formed at the surface but a relatively small amount of weight reduction was observed for FeCrAl-coated TZM alloys up to 60 min of treatment. The post-laser surface treatment following the plasma thermal spray process apparently delayed the severe oxidation process and surface spalling of the alloy. It was suggested that the slow reduction in weight in the post-laser-treated specimen was related to fewer defects in the coating layer. It was also found that a surface reaction layer formed through the diffusion of Fe into the Mo alloy substrate at high temperature. The layer mainly consisted of Fe-saturated Mo and FeMo intermetallic compounds. In order to observe the corrosion behavior of the laser-treated alloy in 3.5% NaCl solution, electrochemical characteristics were also investigated. A proposed equivalent circuit model for the specimen indicated localized corrosion of coated alloy with some permeable defects in the coating layer.

Interfacial microstructure and joining properties of Titanium–Zirconium–Molybdenum alloy joints brazed using Ti–28Ni eutectic brazing alloy

Vacuum brazing of Titanium–Zirconium–Molybdenum (Abbreviated as TZM) alloy using Ti–28Ni (wt%) eutectic brazing alloy was successfully achieved in this study. Reliable TZM brazed joints were obtained at the temperatures ranging from 1000°C to 1160°C for 600s. The interfacial microstructure of TZM joints was characterized by employing SEM, EDS and XRD. The effects of brazing temperature on interfacial microstructure and joining properties were investigated in details. TZM brazed joints mainly consisted of δ-Ti2Ni phase and Ti-based solid solution (Ti(s,s)). The interfacial microstructure of TZM joints was influenced obviously by brazing temperature. Both the thickness of brazing seam and the amount of δ-Ti2Ni phase was reduced with the increasing brazing temperature, while the Ti(s,s) layer did not change significantly. The maximum average shear strength of TZM joints reached 107MPa when brazed at 1080°C. The presence of δ-Ti2Ni intermetallic phase and crack-like structure in joints deteriorated the joining properties, which resulted in the formation of brittle fracture after shear test. In addition, fracture locations were related to the brazing temperature. When the brazing temperature was relatively low, cracks initiated and propagated in the continuous δ-Ti2Ni layer. However, the fracture locations preferred to locating at the interface between TZM substrate and brazing seam when brazing temperature exceeded 1080°C.

Preparation and ductile-to-brittle transition temperature of the La-TZM alloy plates

Powder metallurgy methods were utilized to prepare lanthanum-doped titanium–zirconium–molybdenum (La-TZM) and traditional TZM alloy plates. Tensile and Charpy impact tests were employed to study the room temperature and cryogenic mechanical properties of the two kinds of TZM alloys. For the same process conditions, the lanthanum doping has significantly improved the tensile strength and elongation, which increased by 28.2% and 32.8%, respectively. For these process conditions, the La-TZM has higher density and smaller evenly distributed secondary phases. Compared with TZM, the secondary phase in La-TZM is finer, and hinders the spreading of cracks. This is why the La-TZM alloy plates have higher strength and elongation. By doping lanthanum, the ductile-to-brittle transition temperature of the TZM alloy decreased from −80°C to −120°C. The secondary phase La particles refine the grain and hinder fracture expansion across the grains during the impact fracture of the La-TZM alloy. TZM alloy improved room temperature and cryogenic mechanical properties significantly expand its application range.

Capillary wicking of liquid lithium on laser textured surfaces for plasma facing components

Liquid lithium has been proposed as a coating for plasma facing components (PFC) in fusion reactors in order to reduce recycling and protect the PFCs from high heat loads. Lithium can be introduced onto the surface of the PFCs through a passive capillary wicking mechanism. Surfaces capable of wicking molten lithium to support passive cooling are traditionally produced using a porous material which is added to the surface of a structural material. Laser micro-machining or texturing processes, on the other hand, allow functional surfaces to be applied directly onto existing structural materials. Both 316L stainless steel and titanium–zirconium–molybdenum (TZM) alloys were textured using a Nd:VO4 laser to produce a pattern of open channels with depths between 40μm and 260μm. Screening tests using an isopropanol solution were used to evaluate the ease of wicking for different texturing geometries, and molten lithium wicking experiments were then performed with the samples placed at 45° and 90° orientations. In order to quantitatively measure the progress of the wicking front, a time of flight (TOF) technique, which measures the progress of a temperature gradient using pre-placed thermocouples, was developed to track the progress of the lithium wicking front. The laser textured surfaces on both the 316L and TZM alloys displayed the ability to fully wick both isopropanol and liquid lithium and outperformed commercially available porous materials in the wicking of an isopropanol solution. A comparison of the different texturing geometries on 316L stainless steel samples shows that deeper grooves in the wicking direction combined with shallow grooves, of approximately half the depth, in the cross-channel direction improve the wicking rate and uniformity, and achieve full wetting of the sample surface.

Thermally activated flow stress component of the Mo alloy TZM determined by constitutive models

Using constitutive equations, the activation volume of the particle- and solid solution hardened Molybdenum alloy TZM (Titanium–Zirconium–Molybdenum) was determined by strain rate jump tests to be 130 ± 20 b 3 at approximately 575 ± 48 K, which is comparably high for bcc materials. Furthermore, through this investigation method, other mechanical properties of the thermally activated motion of dislocations in this cubic body centred alloy were additionally determined, such as the height and shape of the Peierls–Nabarro-potential and the activation energy.

Hydrogen damage in friction welded copper joints

The occurrence of hydrogen attack in electrolytic copper and in copper deoxidized with phosphorous, during model heating in oil and in friction welded specimens was investigated. Dissimilar-metal joints, i.e. copper/TZM (titanium–zirconium–molybdenum based alloy) joints and copper/austenitic steel joints, were subjected to microstructural examinations and tensile strength tests. Microcracks near the weld surface, caused by hydrogen attack, were found to occur in the friction welded dissimilar-metal electrolytic copper joints subjected to resoaking at a temperature of 500 °C. This phenomenon did not occur in the joints made using deoxidized copper. The tensile strength of the dissimilar-metal copper joints was tested before and after the additional soaking. It was found that the tensile strength of the friction welded electrolytic copper/steel and electrolytic copper/TZM joints considerably decreased after the additional soaking.

Improvement in Recrystallization Temperature and Mechanical Properties of a Commercial TZM Alloy through Microstructure Control by Multi-Step Internal Nitriding

In order to develop a molybdenum alloy with high recrystallization temperature and excellent mechanical properties, multi-step internal nitriding of a commercial TZM alloy (Titanium–Zirconium–Molybdenum alloy) was studied through optical and transmission electron microscopy, fractographic analysis and three-point bending tests. Two types of nitriding processes, a two-step and another four-step process, were carried out at temperatures between 1423 and 1873 K. Recrystallization was completely suppressed, even at the center of a 1-mm-thick specimen through four-step nitriding, whereas recrystallization proceeded at the specimen center in the case of two-step nitriding. The recrystallization temperature of the TZM alloy in vacuum was raised above 1973 K by four-step nitriding. The ductile-to-brittle transition temperature (DBTT) of the nitrided TZM alloy depended strongly on the thickness of the deformed microstructure. DBTT of the four-step nitriding specimen was below 130 K, which is about 70 K lower than that of the two-step nitriding specimen. The yield stress of the four-step nitriding specimen at 1773 K was about 2.6 times as large as that of the recrystallized specimen.

Discussion

Titanium-zirconium-molybdenum (TZM) alloy was fabricated by using powder metallurgy and rolling techniques. Electrochemical corrosion behavior of the alloy was studied quantitatively using potentiodynamic polarization and scanning electron microscope. Effect of different chloride ions concentrations on corrosion resistance and electrochemical corrosion mechanism on TZM alloy was investigated. Results show that pitting corrosion and intergranular corrosion of TZM alloy mainly occurs in sodium chloride solution. Corrosion generates firstly in the form of pitting corrosion around second phase particles and increases with corrosive media Cl− concentration increasing, and then the intergranular corrosion occurs along grain boundaries and defects. Cl− corrosion can effectively destroy the passive film formed on the sample surface. As the Cl− concentration of corrosive media increases, the corrosion rate of TZM alloy increases until 1.0 mol/L and then decreases. TZM alloy exhibits good corrosion resistance when the concentration of Cl− in corrosive media is 0.5 mol/L or 1.5 mol/L.

Joining ductile refractory metal inserts in x-ray tube targets

Niobium alloy C103 (Nb-10Hf-1Ti) is being investigated for use as an anode shaft material for x-ray tubes. This shaft is used to support the x-ray target and to inhibit heat flow from the target to the rest of the anode. C103 is an attractive shaft material because it has a higher thermal resistance than the conventionally used material—titanium-zirconium-molybdenum (TZM). The primary challenge to using C103 is the joining of the shaft to the powder-metallurgy TZM target. This article discusses a variety of approaches toward accomplishing this, including direct diffusion bonding, the use of a diffusion-enhancing interlayer, and the incorporation of a ductile metal insert into the x-ray target.

Chemical compatibility studies of GaAs and CdZnTe with the alloys WC-103 and TZM

The objective of this study was to determine the chemical compatibility of gallium arsenide (GaAs) and cadmium zinc telluride (CdZnTe) with WC-103, a niobium hafnium titanium alloy, and TZM, a titanium zirconium molybdenum alloy. Compatibility in these systems is of primary interest for crystal growth experiments during space shuttle missions. Crystal growth ampoules containing GaAs and CdZnTe must be encased in a sample ampoule cartridge assembly (SACA) during crystal growth, which is qualified as a level of safety containment. Two of the primary metal candidates for these containment cartridges for experiments conducted aboard the USML-1 shuttle mission were WC-103 and TZM. Reaction couples between the semiconductors and the metals were constructed and used to simulate failure of the growth ampoule. Experiments were designed to examine various stages of failure including the worst case situation, in which failure occurred at the beginning of the growth experiment. The couples were analyzed optically and using the scanning electron microscope to evaluate any metal loss or reaction products formed.