Titanium-zirconium-molybdenum Alloy Research Articles

TZM Alloy Job Carrier for High Temperature Vacuum Furnace

RRCAT has a cold walled dry pumped controlled atmosphere furnace for brazing, diffusion bonding and heat treatment of components required for particle accelerators. This furnace has a work zone of 500 mm diameter and 1.5 meter length and it can be operated up to a temperature of 1100 deg C. A Titanium-Zirconium-Molybdenum (TZM) alloy job carrier has been designed for a load carrying capacity of 400 kg for better utilization of the vertical space. Due to alloy’s outstanding combination of properties e.g. high electrical and thermal conductivity, low coefficient of thermal expansion and high rupture as well as creep strength; it is a preferred choice in a wide variety of high-temperature applications in spite of its higher cost. The structural design of the job carrier needs optimization in order to reduce its weight as well as its cost without compromising on design constraints. In this paper, a detailed design of job-carrier has been presented using plate theory and Euler beam theory. Subsequently, finite element analysis (FEA) in ANSYSTM Workbench is performed to ensure that resultant stresses and deformation are within acceptable limits. Additionally, a limit load analysis has been performed to determine the maximum load capacity and factor of safety. FEA results are then used for fatigue life and creep assessment. The job-carrier has been successfully installed inside RRCAT’s controlled atmosphere furnace and has been tested at full load. The effort has also led to 70% reduction in the procurement cost with respect to commercially available products.

Effect of Al content on 1200 °C steam oxidation behavior of Cr-based coatings on TZM alloy

In this paper, the 1200 °C high temperature steam oxidation behavior of Cr-based coatings with different Al content (0, 15 at%, 30 at%, 50 at%) deposited on titanium-zirconium-molybdenum (TZM) alloy has been investigated. The oxidation resistance of TZM alloy is significantly increased by the Cr-based coatings. The Cr70Al30 coating exhibits the best performance due the protectiveness of a triple oxide layer formed on coating surface, including outer Al2O3 and Cr2O3 mixed layer, intermediate Cr-rich oxide (Cr2O3) layer and inner Al-rich oxide (Al2O3) layer. The effect of Al content on the oxidation resistance of Cr-based coatings is discussed in detail.

The formation mechanism of micro-nano secondary phase in solid-liquid doped TZM alloy

Among the various secondary phases distributed in the TZM (Titanium-Zirconium-Molybdenum) alloy matrix, the ones that can play a strengthening role are often those with a particle size smaller than 1 μm. In this study, titanium sulfate, zirconium nitrate, and fructose were used as raw materials. The TZM alloy with uniform distribution and an average secondary phase particle size of 940 nm (hereinafter referred to as MN-TZM alloy) was prepared through a solid-liquid doping preparation process. The thermodynamic calculation reveals the formation mechanism of the micro-nano-level secondary phase in the MN-TZM alloy. Thermogravimetric analysis (TG-DSC, TG-MS) and transmission electron microscope (TEM) confirmed the calculation results. The generation process of the micro-nano secondary phase evolution can be divided into four parts. The first stage is the process of solute dissolution at room temperature. In the second stage, doping and drying process take place below 100 °C. Third, reduction and secondary phase precursor incubation processes occur from 100 to 700 °C. Fructose decomposes (100 °C) to obtain organic carbon and water. The decomposition of zirconium nitrate (100 °C) yields NH 3 , H 2 O, ZrO 2 and Zr, while the titanium sulfate decomposes directly at 200– 242 °C to obtain SO 2 , H 2 O, TiO 2 and Ti. In the last stage, the secondary phase nucleates and grows up (700– 1800 °C). A large variety of micro-nano-scale and even nano-scale secondary phase particles have been discovered, including TiO 2 , ZrO 2 , ZrC and TiC. These observations provide necessary information for tracing back the secondary phase precipitation mechanism in the manufacturing process of high-performance molybdenum alloys. • The average grain size of MN-TZM alloy is 940 nm. • The micro-nano secondary phase reduces the average grain size of TZM alloy by 26%. • TZM alloy was prepared from titanium sulfate, zirconium nitrate, fructose and molybdenum powder for the first time. • The formation mechanism of micro-nano secondary phase in TZM alloy was clarified.

Precise control of oxygen for titanium-zirconium-molybdenum alloy

Organic carbon has been used as a reducing agent to reduce the oxygen content in the TZM (Titanium-Zirconium-Molybdenum) alloys for the first time. The TZM alloys were prepared by the powder metallurgy sintered by hydrogen and vacuum, respectively. With increasing the organic carbon content from 0.04 wt% to 0.8 wt%, the influence of organic carbon content and sintering methods on the oxygen content of TZM alloys and their action mechanism were studied. The results show that the oxygen content of TZM alloy sintered by hydrogen decreases significantly with the increase of organic carbon. The oxygen content is as low as 300 ppm when the organic carbon is 0.8 wt%. The oxygen content of the TZM alloy varies between 50 ppm and 110 ppm under vacuum sintering. When the oxygen content decreases, the secondary phase particles precipitated in the alloy decrease the alloy's hardness due to the weakening effect of solution strengthening and secondary phase strengthening. The density of TZM alloy decreases with increasing organic carbon, whether in vacuum or hydrogen sintering. Verification experiments confirm the accuracy of the conclusion. As the oxygen content decreases from more than 3000 ppm to less than 1000 ppm, the secondary phase particles in the TZM alloy changed from mostly TiO2 and ZrO2 to Ti/Zr composite oxide particles containing zirconium-rich stripes. In the state of the lowest oxygen content, only zirconia was found in the matrix

Effect of Ti Content on Microstructure and Wear Performance of TZM Alloys Produced by Mechanical Alloying Method

In this study, changes in microstructure, hardness and wear performance of titanium–zirconium–molybdenum (TZM) alloys produced by mechanical alloying method with the addition of different amounts of titanium (Ti) were investigated. Mechanically alloyed powders were sintered at 1300 °C for 4 h under 10–6 mbar vacuum environment. The produced alloys were characterized by scanning electron microscope (SEM + EDS), X-ray diffraction, grain size distribution, hardness and density measurements. In the wear tests, three different loads and five different sliding distances were used. Results showed that the produced TZM alloys were porous, and the pores in the alloys containing 0.40% and 0.45% Ti were generally located on the grain boundaries. In alloys containing 0.50% Ti, inside the grain the pore sizes increase, while in the alloy containing 0.55% Ti, the pore sizes in grain boundary decrease. Grain size distribution results show that as the Ti content increased, the amount of grain size over 6 µm decreased and smaller than 6 µm increased. Hardness and density results show that while the hardness of TZM alloys produced increases depending on Ti content, their density decreases. The highest hardness was obtained in the TZM alloy containing 0.55% Ti, while the lowest density was obtained in the same alloy. Wear test results show that the lowest weight loss was obtained in TZM alloy containing the highest amount of Ti (0.55%) under all loads.

Analysis of microstructure and mechanical strength of lap joints of TZM alloy welded by a fiber laser

The application of molybdenum alloys to structural components is severely limited due to their poor weldability with serious defects of porosity and joint embrittlement after welding despite their high melting temperature, hot strength and creep resistance. A systematical experimental study has been conducted to explore the potential of laser welding of 0.5 mm-thick Titanium-zirconium-molybdenum (TZM) alloy in a lap welding configuration. Porosity was found to be the most serious problem in the TZM laser lap welding process. Introducing an interface gap of 0.09 mm had the most positive effect in reducing the porosity compared to using helium gas, different shielding gas flow rates, adding alloy element and different heat input rate. With the use of 0.09 mm-interface gap, the porosity of the weld joint was reduced to 3%. The tensile stress of the bead on plate (BOP) welded joint could achieve about 60% that of the base metal. The fracture stress of the lap welded joint obtained by using 0.09 mm-interface gap in tensile-shear test was about 142 MPa. The porosity and embrittlement were responsible for the reduction of the strength and ductility of the welded joint.

Electrochemical Corrosion Behavior of Titanium-Zirconium-Molybdenum Alloy

Titanium-zirconium-molybdenum (TZM) alloy and rare earth lanthanum doped La-TZM alloy were fabricated using powder metallurgy and rolling technique. Their electrochemical corrosion behavior was studied quantitatively using potentiodynamic polarization, scanning electron microscope and energy spectrum techniques. Their corrosion behavior was investigated in neutral, acidic and alkaline medium, while keeping the Cl − concentrations invariant. The results show that the corrosion resistance of the tested TZM alloy is better than that of the La-TZM alloy in neutral and alkaline media, while in an acidic medium, the La-TZM alloy is better. It is also found that the alloys are more corrosion-resistant in an acidic medium than in a neutral medium, and are the least corrosion-resistant in an alkaline medium. Finally, we find that Cl − effectively destroys the passivation film formed on the corrosion surface; OH − and Cl − double erosion promoted these two types of alloy intergranular corrosion increased.

High temperature mechanical properties of TZM alloys under different lanthanum doping treatments

La(NO3)3 and La2O3 doped titanium-zirconium-molybdenum (TZM) alloys were fabricated by using powder metallurgy method, and their room and high temperature mechanical properties were studied in this paper. Results show that the mechanical properties of La(NO3)3-TZM alloy sheet is better than that of La2O3-TZM alloy sheet in room temperature and the high temperature mechanical properties of both alloys have similar change trend but different sensitivity of temperature. The tiny grains in La(NO3)3-TZM alloy sheet is more sensitive to temperature and the lanthanum doping significantly influences the temperature sensitivity of the alloy. When the temperature is lower than 1400 °C, both TZM alloy sheets present a transgranular fracture mode. It is ductile intergranular fracture mode when the temperature is higher than 1400 °C, and the temperature of fracture mode transition is 1400 °C.

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.

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.

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.

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.