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Pure molybdenum sheets were prepared by powder metallurgy and unidirectional rolling process. The microstructure, texture, grain orientation, mechanical properties and fracture mechanism of sintered samples were investigated. The results show that tensile strength and microhardness of 95% rolled sheet are 1028.095 ± 19.32 MPa and 323.2 ± 11.68 HV. The main texture components of (011)〈110〉 is Goss texture with reduction in the range of 70–95%. Two grain orientations of 〈111〉 fiber & 〈100〉 fiber and 〈100〉 fiber & 〈110〉 fiber are formed in the 47% and 95% rolled molybdenum sheets, respectively. Meanwhile, the fiber structure become more refined and oriented in the rolled molybdenum sheets when the rolling reduction is >87%. Brittle characteristics show typical cleavage failure. • Tensile strength and microhardness of 95% rolled sheet are 1028.095±19.32 MPa and 323.2±11.68 HV. • The main texture intensity value of Goss texture is 9.52 in the 95% rolled sheet. • Two grain orientations of <111> fiber & <100> fiber and <100> fiber & <110> fiber are formed in the 47% and 95% rolled molybdenum sheets, respectively. [ABSTRACT FROM AUTHOR]

Due to the unique microstructure, nanoporous materials, have great potential application in the fields of catalysis, sensing and fabrication of advanced materials. This study mainly focuses on the thermal decomposition mechanism of ammonium paramolybdate and nanoporous flake molybdenum powder fabrication. The decomposition process was clarified and verified. The approximate molar formation enthalpy and some thermodynamic data of ammonium paramolybdate and its related decomposition products under experimental conditions were estimated by enthalpy change values of decomposition reaction in the various stages. Nanoporous flake molybdenum powder was fabricated by sol-gel reduction method at different pH values. The mechanism of transition from ammonium paramolybdate to molybdenum powder was elucidated. The results show that the morphology of products in each stage is hereditary. With the increase of pH value, the reaction was complete and the powder morphology gradually became flake and the shape distribution was uniform and distribution. When the pH is 5, through inert gas passivation treatment, the final molybdenum powder has a uniform particle size of about 65 nm and a specific surface area of about 7.5 m2/g. The nanoporous powder with such a special morphology and microstructure has potential prospects in the field of functional materials such as catalysis. • Heredity was found in the mechanism of AHM to Mo transformation. • CA can not only be used as complexing agent, but also control the pH value of the solution. • The morphology of MoO 3 and Mo particles gradually became flakes with the increase of pH value. • Inert gas passivation can reduce and concentrate the PSD and decrease agglomeration. • Nanoporous flaky Mo powder was prepared by sol-gel reduction method with high specific surface area. [ABSTRACT FROM AUTHOR]

This paper investigates the mechanism of crack generation and propagation in laser-welded joints of Mo 14Re alloy plates. The study utilized optical microscopy (OM) and scanning electron microscopy (SEM) to examine the microstructure and morphology of the crack area in the Mo 14Re laser-welded joint. Additionally, energy dispersive spectroscopy (EDS) was employed to characterize the elements at the crack defect, while electron backscatter diffraction (EBSD) was utilized to analyze the grain boundary and crystal orientation at the crack defect.The analysis of crack formation and propagation considered various factors, including grain boundary segregation, characteristics of grain boundaries and crystal orientation, and the Schmidt factor. The findings revealed that cracks formed in the weld area exhibited distinct characteristics of brittle fracture along the grain. Notably, these cracks displayed evident carbon and oxygen segregation attributed to the presence of a low melting point eutectic liquid film. The segregation, along with high-temperature compounds on the fracture surface, emerged as the primary factors contributing to crack formation.In the proximity of the crack, there exists a concentration of strain, inducing plastic deformation and thereby facilitating crack initiation. Cracks exhibit a tendency to originate along large-angle grain boundaries and deflect along these boundaries. Owing to the difference in atomic slip characteristics on both sides of the crack, the direction of crack propagation is more inclined to deflect towards grains with a smaller Schmidt factor. • The comprehensive mechanism of crack generation and propagation is proposed. • Grain boundary segregation plays a leading role in the generation of cracks. • Cracks always tend to propagate towards grains with small Schmidt factors. [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]

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]

Microstructure and texture evolution of pure molybdenum prepared by powder metallurgy during the thermal mechanical processing were studied. Uniaxial compression tests were carried out on Gleeble-1500 thermal mechanical simulator in range of temperature (1100 ºC-1300 °C), strain rates (0.1 s−1-10 s−1) and true strain (0.3–0.6), respectively. The results show that the difference in deformation mechanism caused by temperature, strain rate and true strain has a great influence on microstructure and texture. Especially at 1300 °C, pure molybdenum will have obvious geometric dynamic recrystallization, and as the deformation progresses, the jagged high angle grain boundaries are close to each other and forming an equiaxed crystal. This equiaxed crystal structure is separated by a high angle grain boundary and the size of the equiaxed crystal is close to the subgrain size. In addition, this paper focuses on the deformation behavior of pure molybdenum under different true strains. There are two typical orientations of fiber texture. One is <100>//CD fiber texture, including {001} <100> cube texture and {110} <001> goss texture; other is <111>//CD fiber texture, including {112} <111> copper texture and {110} <111> texture. The increased distortion of the deformation provides a certain driving force for the rotation of the grain, prompting it to the preferred slip system, thereby weakening the texture resulting from the deformation. What's more, the dynamic recrystallization behavior can significantly weaken deformed textures, especially for <111>//CD fiber texture. • This is the first study of the texture evolution of hot deformed pure molybdenum, especially at different strains. • The effects of temperature, strain rate and strain on the thermal deformation of pure molybdenum are described in detail. • Significant geometric dynamic recrystallization occurs when deformed at 1300 °C. [ABSTRACT FROM AUTHOR]