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The 1.0 wt% La - doped molybdenum - 0.6 wt% titanium - 0.11 wt% zirconium (La-TZM) alloy has a maximum tensile strength of 1350 MPa and elongation to failure of 7.5%, at room temperature. In this paper, the fracture behavior of this La-TZM alloy was studied. The La 2 Ti 2 O 7 phase produces micro-cracks during rolling deformation which eventually propagate to full cracks during tensile testing. The reason for the La-TZM fracture is deformation incompatibility and large stress concentrations at the La 2 Ti 2 O 7 particles inducing particle cracking, leading to micro-cracks along the grain boundaries. The La 2 Ti 2 O 7 phase is composed of 69.8 at.% O - 13.3 at.% Ti - 0.6 at.% Zr - 10.4 at.% La and is formed by the La 2 O 3 , TiO 2, and ZrO 2 secondary phases when sintered above 1350 °C. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 TiO 2 and ZrO 2 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 [Display omitted] • Reveals the control mechanism of oxygen content of TZM alloys • Too much oxygen in TZM alloy will cause the second phase particles to be coarse. • The microstructure of TZM alloy changes with the change of oxygen content. • The verification test confirmed the accuracy of the mechanism. [ABSTRACT FROM AUTHOR]

Mo–TiC–La 2 O 3 molybdenum alloys were strengthened and toughened by the synergistic action of nano-carbide particles and rare earth oxides. In this paper, the Mo–TiC–La 2 O 3 alloy system was prepared by powder metallurgy. The microstructure was characterized by optical, scanning, and transmission electron microscopy. The mechanical properties were tested using the hardness tester and universal tensile testing machine. The grain size of the Mo–TiC–La 2 O 3 alloy is smaller than the Mo–TiC and Mo–La 2 O 3 alloys. The strength and elongation of annealed Mo–TiC–La 2 O 3 alloy are 1291 MPa and 6.6%, respectively. The strength and ductility of the annealed Mo–TiC–La 2 O 3 alloy are higher than the Mo–TiC and Mo–La 2 O 3 alloys. According to the interfacial mismatch between the secondary phases and the matrix, along with oxygen impurities interactions, the mechanisms of strengthening and toughening of the secondary phases in the Mo–TiC–La 2 O 3 alloy were revealed. • The strength of alloys increases from Mo–La 2 O 3 to Mo–TiC, to Mo–TiC–La 2 O 3. • Mo–TiC–La 2 O 3 alloy not only has a high hardness, the high tensile strength, but also 6.59% elongation. • Mo–TiC–La 2 O 3 alloy strengthening from nano-TiC, TiO 2 , and La 2 Ti 2 O 7 phases and toughening from La 2 O 3. [ABSTRACT FROM AUTHOR]

Due to alloying elements' influence, it is difficult for TZM alloys to simultaneously control the carbon content and oxygen content during the hydrogen sintering. In this paper, the preparation process of TZM alloy is studied, the carbon content and oxygen content of the preparation process are detected, and the control mechanism of the carbon and oxygen content is clarified. The carbon and oxygen content of TZM alloy is controlled at 30 ppm and 70 ppm, respectively. The existence form of oxygen and the evolution mechanism of oxygen during the preparation of TZM alloy were studied. The results show that when the oxygen content of the TZM alloy is about 2000 ppm, there are many secondary phases located in the grain boundary, and its main component is TiO 2 (containing a small amount of ZrO 2). With the oxygen content of the TZM alloy decreases, the number of secondary phases decreases, the size becomes smaller, and the Zr content in the composition gradually increases. When the oxygen content of TZM alloy is 70 ppm, there is no apparent secondary phase in the alloy, the main chemical composition of the secondary phase is ZrO 2 , and fracture mode of the alloy changes from intergranular fracture to intergranular and transgranular mixed fracture. As the oxygen content of TZM alloy decreases, the titanium and zirconium elements can be better solubilized in the molybdenum matrix. The alloy's primary strengthening mode gradually changes from the secondary phases strengthening to the solid solution strengthening. • The carbon and oxygen content of TZM alloy is controlled at 30 ppm and 70 ppm, respectively. • The oxygen content of TZM alloy affects the chemical composition of the secondary phases. • Oxygen content affects the dominant strengthening mode of sintered TZM alloy. • The oxygen content of TZM alloy can be effectively controlled by eliminating the " internal getter " effect. [ABSTRACT FROM AUTHOR]

The high-temperature tensile properties and microstructures of as-processed (forged and rolled) TZM alloy were studied during thermoplastic deformation by uniaxial tensile tests at different annealing temperatures (850–1450 °C). The recrystallization phenomenon observed for rolled TZM alloy about 1300 °C and forged TZM alloy about 1400 °C. The forged state as an example, the annealing forged TZM alloy performed cup-shaped fracture by SEM being stretched at 1600 °C and studying the initiation, aggregation and growth of micropores during the fracture process were performed. ODF map was used to accurately prove the orientation distribution density in any orientation of forged TZM alloy space after annealing. The activation of the forged TZM alloy sliding system was related to the structure of the material, the deformation method and the force direction. Meanwhile, the high-resolution Electron backscatter diffraction (EBSD) technique was used to study thermoplastic deformation behavior and microstructure evolution of forged TZM alloy under different annealing temperatures in Channel5 software, getting a deeper deformation mechanism of forged TZM alloy during thermal deformation. • As-processed TZM alloy were annealed for different temperatures observed by SEM. • The micro-hole aggregation and growth of fracture was used to explain ductile crack behavior through tensile test. • Strength and plasticity of forged TZM alloy could be increased by tensile test after annealing than rolled TZM alloy. • {112}<111> was greater than {110}<111> slip system in neck area for forged TZM alloy according EBSD technology. [ABSTRACT FROM AUTHOR]

The size of the secondary phases affects the lanthanum-doped titanium‑zirconium‑molybdenum (La-TZM) alloy properties. In this study, the microstructure and mechanical properties of the La-TZM alloys were regulated by adding carbon and Ti/Zr elements, which resulted in different secondary phase characteristics. Adding nano-TiC and ZrC decreased the micron secondary phase size of the La-TZM alloy by 26.7%, and increased the yield strength by 27%, reaching 1239 MPa. The effects of secondary phase size and distribution on yield strength were analyzed. This study contributes to the design and theoretical analysis of new molybdenum alloys. • Average size of micron secondary phases doped nano-TiC/ZrC is reduced by 26.7%. • The yield strength of doping nano TiC-ZrC alloy improved 22.6%, reaching 1239.42 MPa. • The effect of secondary phase size on yield strength were calculated. • The effect of secondary phase distribution on grain size were analyzed. [ABSTRACT FROM AUTHOR]

Previous experimental studies in the Mo-TiC-ZrC-C (TZM) alloy have shown the existence of secondary phases around the composition TiC, ZrC, TiO 2 , ZrO 2 and ZrTiO 4. No research about the interface of secondary phases and Mo matrix was indicated. We characterized the different secondary phases influence on the structure and mechanical properties by the mismatch and electron density. And discovered that ZrTiO 4 has largest lattice misfit and electron density, contributing to better strengthening and toughening of TZM alloy. The ZrTiO 4 interface bonding strength is superior to the other secondary phases. This new understanding opens opportunities for designing high strengthening-toughening Mo alloy. Unlabelled Image • The effect of addition of TiC and ZrC on the strength and elongation of Mo-TiC-ZrC-C is studied • The composition 0.08%TiC-0.11%ZriC-0.06%C showed high strength of tensile strength 1292.65 Mpa and elongation 6.9%. • ZrTiO 4 has largest lattice misfit and electron density, contributing to better strengthening and toughening of TZM alloy. [ABSTRACT FROM AUTHOR]