The refractory metal molybdenum not only has excellent thermal conductivity, electrical conductivity and corrosion resistance, but also has low thermal expansion coefficient, high hardness and good high-temperature strength, so it is widely used in electronic industry, aerospace industry, energy industry and other fields. However, at room temperature, pure molybdenum has some disadvantages such as brittleness, poor machining performance, poor welding performance, easy oxidation and recrystallization brittleness, which limit the application of pure molybdenum. Adding a certain amount of alloying elements such as C,B,K,Si,Al,Re and rare earth elements is an effective method to improve the brittleness of molybdenum. Among them, rhenium is the most prominent alloying element. The addition of rhenium can not only improve the property of molybdenum at room temperature and welding, but also improve the property of molybdenum at high temperature.
Powder metallurgy and vacuum smelting are generally used to prepare molybdenum-rhenium alloy billets. When the rhenium content is lower than 9%, the rhenium in the solid solution of molybdenum forms the phase with the body core cubic structure, and the lattice constant of molybdenum decreases. When the rhenium content higher than 9%, forming Χ and sigma phase. The melting point, thermal and electrical properties of molybdenum-Rhenium alloy are between that of pure molybdenum and pure rhenium, and Rhenium can increase the recrystallization temperature of molybdenum and reduce its plastic brittle transition temperature. Rhenium can improve both the strength and the plasticity of molybdenum. The processing hardening rate of molybdenum-rhenium alloy was between pure molybdenum and pure rhenium and close to pure molybdenum.
Molybdenum alloys with 2% ~ 5% rhenium as the base. Rhenium can improve the plasticity and strength of molybdenum by adding molybdenum, which is a solid solution strengthened alloy. With 35% rhenium in molybdenum, the rolling deformation can reach 90% at room temperature. Molybdenum-rhenium alloy was prepared by powder metallurgy. Mo-Re alloy can be used as high-speed rotating X-ray tube target material, long life grid plate for microwave communication, space reactor core heating tube, high temperature furnace heating element, high temperature thermocouple, etc. The tensile strength, ductility and resistivity of molybdenum-rhenium alloy increased with the increase of rhenium content. Mo-5%Re and Mo-41%Re are usually used as thermocouple wires for structural materials in aerospace. Mo-50%Re is used as high temperature structural material.
The effect of Rhenium on molybdenum: Rhenium can form MoReO4 compound with Molybdenum, which is different from MO2 compound and does not infiltrate grain boundary. Rhenium can improve the solubility of C and O, which makes carbide and oxide difficult to be separated out. The twin-deformation of molybdenum-Rhenium alloy at low temperature is different from that of pure molybdenum. Rhenium changes the electronic structure of molybdenum, reduces the direction of atomic bond, reduces the stacking fault energy, and increases the shear modulus.
