Molybdenum-molybdenum diffusion welding with Ti foil intermediate layer
is a silvery white metal with good thermal and electrical conductivity, low thermal expansion coefficient and low steam. It has become an important material for electronic and electric equipment manufacturing, metal material processing industry, glass manufacturing, high-temperature furnace structural parts manufacturing, aerospace and national defense industry applications. In addition, molybdenum on molten glass, molten salt and molten metal corrosion resistance is higher, and is used as a large number of high temperature furnace heating materials and structural materials, vacuum tube large electrodes and gate semiconductor and electric light source materials. With the increasingly wide application of molybdenum and the complex shape of structural devices, the effective connection between molybdenum and molybdenum metal matrix is not only of academic value, but also opens up a feasible way for the further application of molybdenum metal. Diffusion connection is a welding method in which the welding parts are placed in vacuum or protective atmosphere, under the action of pressure and temperature at the same time, the microscopic protrusion of the welding surface produces plastic deformation to achieve close contact, and then the whole solid connection is formed through atomic diffusion. Due to the relatively high melting point of the key metal, the vacuum diffusion welding of molybdenum matrix must be carried out at a higher welding temperature, which is very unfavorable to the welding of structural parts. To achieve welding by atomic diffusion at lower temperatures, interlayer metals with relatively low melting points are usually added, and the interlayer metal and the base metal are joined by diffusion. When Ni is used as the intermediate layer, Mo-Ni connection is made at 900°C, and then Mo-Ni and Al connection is made at 550°C to obtain the best connection strength. When Ti is used as the interlayer material, Mo-Al foil is welded by direct diffusion, and the bonding rate reaches 100%.
Select 5 microns Ti foil for the middle tier, Mo Mo - diffusion welding under the condition of vacuum, the interface morphology using scanning electron microscopy (SEM) observation, and use its own X-ray spectrometer on the middle tier of the interface element diffusion and elemental composition of regional test and analysis, to study the interface morphology, diffusion and interface bond quality.
(1) The vacuum diffusion welding between molybdenum and molybdenum matrix was successfully realized under the technological conditions of 1000°C, 10MPa and 60 min with the addition of 5μm Ti foil as the intermediate layer, and the welding rate was 100%.
(2) Based on the infinite mutual solubility of Mo-Ti and the strong diffusion ability of Ti atoms, Mo-Ti solid solution was generated across the whole thickness direction of Ti foil, and its composition was nearly uniform. The original Ti layer formed a Mo-Ti solid solution layer with nearly uniform composition.
