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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]

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 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]