Molybdenum rhenium alloy
Molybdenum rhenium alloy is a kind of alloy composed of molybdenum and rhenium. The alloy shows rhenium effect to improve plasticity. The rhenium content in the alloy is generally 11% ~ 50% (mass fraction).
The refractory metal molybdenum not only has excellent thermal conductivity and corrosion resistance, but also has low thermal expansion coefficient, high hardness and good high temperature strength. Therefore, molybdenum has a wide range of applications in the fields of electronic industry, aerospace industry and energy industry. However, pure metal molybdenum is brittle at room temperature, poor processability, poor welding performance, easy oxidation, recrystallization brittleness and other shortcomings, all of which limit the application of pure metal molybdenum. Adding a certain amount of alloying elements such as C, B, K, Si, Al, re and rare earth elements is an effective way to improve the brittleness of molybdenum. Among them, rhenium is the most prominent element. The addition of rhenium can not only improve the room temperature performance and welding performance of molybdenum, but also improve the high temperature performance of molybdenum.
Molybdenum rhenium alloy ingots are usually prepared by powder metallurgy and vacuum melting. When rhenium content is less than 29%, rhenium forms a BCC α phase in molybdenum, and the lattice constant of molybdenum decreases. When rhenium content is higher than 29%, a phase and a phase are formed. The melting point and recrystallization temperature of pure Re and Re alloy are between those of pure RE alloy and RE alloy. Rhenium can improve the strength and plasticity of molybdenum. The work hardening rate of molybdenum rhenium alloy is between pure molybdenum and pure rhenium, but close to pure molybdenum.
Molybdenum alloys with 2% - 5% RE were added. The addition of rhenium to molybdenum can improve the plasticity and strength of molybdenum. When 35% rhenium is added into 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 target material of high-speed rotating x-ray tube, long-life grid plate for microwave communication, core heating tube of space reactor, heater of high-temperature furnace, high-temperature thermocouple, etc. The room temperature tensile strength, ductility and resistivity of molybdenum rhenium alloy increase with the increase of RE content. Mo-5% Re and Mo-41% Re are usually used as thermocouple wires and structural materials in aerospace. Mo-50% Re was used as high temperature structural material.
The effect of rhenium on molybdenum: rhenium and molybdenum can form moreo4 type compound, which is different from Mo2 type compound and does not infiltrate the grain boundary; rhenium can improve the solubility of C and O, so that carbides and oxides are difficult to precipitate; molybdenum rhenium alloy twinning deformation occurs at low temperature, which is different from pure metal molybdenum; rhenium changes the electronic structure of molybdenum, reduces the direction of atomic bond and reduces stacking fault energy, Increase the shear modulus.
