Mo-W alloys have been developed for their ability to resist chemical corrosion and are used as low-cost and lightweight alternatives to pure
tungsten. Mo-Re alloys have very low plasticity - brittleness transition temperature due to the rhenium effect.
Dispersion-strengthened
molybdenum alloys doped with Al, K and Si, such as MH and KW, can stabilize the forging microstructure, prevent the recrystallization or stabilize the elongated recrystallized grain structure, avoid the transformation to equiaxed grain, and significantly improve the low temperature plasticity because of the fine dispersion produced by the original powder. The doped MH and KW molybdenum alloys have excellent creep resistance and extremely high recrystallization temperature, although they have no special improvement in strength at low temperature. In addition, active metal oxide dispersion phase is also used to improve the high strength and creep resistance of molybdenum, such as Z-6 molybdenum alloy is added 0.5%ZrO2 to disperse strengthening. It is provided by the stable grain structure of ZrO2, and the improvement in creep rate is similar to the effect played by dopants. Recently, the strengthening of rare earth oxide molybdenum alloy has been studied. The molybdenum alloy with 0.2%~0.3%La2O3 added can reduce the intergranular fracture due to the dislocation of La2O3 in the second phase, which improves the fracture strength and improves the low temperature brittleness. Another example is the addition of Y2O3 molybdenum alloy, such as ZHMR, with the addition of Y2O3 from 0 to 1.5%, its hardness, tensile strength at room temperature, compressive strength are increased.
In addition to the above strengthened molybdenum alloy, in order to improve the oxidation resistance of molybdenum, Al, Ni, Si and other elements are often added. For example, when 0.17%Al is added to molybdenum, its oxidation resistance is improved compared with that of pure molybdenum. When 30%Ni and 20%Co are added to molybdenum, the oxidation resistance life of molybdenum can reach more than 100h at 940℃.Molybdenum and silicide combine to form molybdenum silicide is a kind of material with good resistance to high temperature oxidation. As a heating element, molybdenum silicide can continue to be used when heated to 1600~1700℃ in the air. However, molybdenum silicide is brittle and difficult to be processed, so it has not been widely used.
