Molybdenum alloy has excellent high temperature strength and mechanical stability (up to 1900°C). Their high ductility and toughness provide a defect that has greater tolerance than ceramic brittle fracture.
Types of molybdenum alloys
1. TZM and TZC molybdenum alloy
TZM alloy is a molybdenum-based alloy containing 05% Ti, 0.08% Zr and 0.01% ~ 0.04% C. Because a small amount of finely dispersed particle additives prevent molybdenum from growing in high temperature conditions, it significantly improves high temperature strength and Anti-recrystallization temperature. TZC alloy is an alloying element with a higher content of molybdenum alloy than TZM alloy. It is an improved variety of TZM molybdenum alloy. It has a better strengthening effect of aging heat treatment. However, due to the high cost of TZC alloy and difficult processing, it has not replaced TZM alloy.
Compared with pure molybdenum, TZM (or TZC) alloy has a higher recrystallization temperature and high-temperature strength, so TZM molybdenum alloy is often selected as mold casting tools and high-temperature furnace components, such as support frames, boats and trays. In the glass industry, TZM alloy replaces low-carbon pure molybdenum materials, because in the manufacture of glass, the temperature> 1400 ℃, the active metal carbide will not decompose, thus preventing the formation of bubbles, improving the quality of glass products, and extending the molybdenum electrode Life. In addition, TZM alloy can also be used for extrusion dies of aluminum alloy and Ag-Cd alloy, anvils for hot upsetting, guide electrodes, forging dies and nozzles.
2. MHC and ZHM alloy
The molybdenum alloy is strengthened by adding Hf instead of Ti to form a dual-phase structure. ZHM has better performance than MHC. The properties of the alloy have a lot to do with the degree of deformation and heat treatment conditions. For example, in the MHC series, Mo-1Hf-0.05C alloy ingots made of powder metallurgy, when the forging deformation reaches 60%, the tensile strength at 950~1250℃ is 20% higher than that of TZM. The elongation in each direction is 1%~10%.
There are ZHM4 (Mo-1.2Hf-0.4Zr-0.15C) in the ZHM series; ZHM6 (Mo-1.5Hf-0.5Zr-0.19C); ZHM7 (Mo- 1.8Hf-0.6Zr-0.23C); ZHM8 (M- 2.1Hf-0.7Zr-0.27C) Four-component alloy. These alloys have excellent processing properties, good high temperature strength and low temperature ductility.
3. Mo-W alloy
Alloying with tungsten improves the heat resistance of molybdenum. Since 25%~30%W is added, the working temperature of the alloy increases by about 200℃. Mo-W alloy can only be produced in the form of parts, not plates and wires. Mo-W alloy has a slightly higher recrystallization temperature than pure molybdenum. It has excellent corrosion resistance to molten zinc, so its main application is in the zinc industry, such as pump components, casting valves, siphons and nozzles on automatic die casting machinery.
Four. Mo-Re alloy
Although rhenium is scarce and expensive, it is not only used in the electronics industry because of its unique high thermal temperature and good plasticity comprehensive properties. Mo-5Re and Mo-41Re are usually used as thermocouple wires and structural materials in aerospace. Mo-50Re is used as high temperature structural material.
5. MH and KW molybdenum alloy
In order to solve the problem of molybdenum sagging at high temperatures, molybdenum is usually doped with K, Si, and Al to increase its recrystallization temperature. Due to the fibrous structure of doping and one-way fierce processing, the recrystallization temperature is increased from 1400℃ of pure molybdenum to about 1800℃. In use, it still maintains ductility even at the recrystallization temperature. The creep rate of doped molybdenum at 1800℃ is about 1000 times lower than that of pure molybdenum, which is not only better than pure molybdenum but also better than TZM and rare earth elements and oxide The performance of molybdenum alloy, so the parts made with it remain dimensionally stable even at high temperature.
In terms of strength properties, doped molybdenum shows great advantages under high temperature conditions. Although below 1000 ℃, the strength of TZM and pure molybdenum are higher than doped molybdenum. This means that the higher the temperature, the more effective the bubble strengthening.
Doped molybdenum has some typical applications due to its superior properties, such as plastic support wires in automobile and motorcycle headlights, electron tubes and furnace heating elements, boats for sintering and annealing, etc.
Application of unique properties of molybdenum alloy:
High temperature heating elements, radiation shielding, extrusion, forging molds, etc.;
Rotating fluoroscopy anodes for clinical diagnosis;
Anti-melting glass for glass melting furnace electrodes and components;
Silicon semiconductor chip heat sink mount that matches the thermal expansion coefficient;
Sputtering layer, only Angstroms (10-7 mm) thick, interconnects the gate and the integrated circuit chip;
Car piston rings and machine parts are sprayed with paint to reduce friction and improve wear.
Molybdenum and other metal alloys are used in other applications:
Molybdenum tungsten alloy is made of special zinc liquid resistant;
Molybdenum copper package provides low expansion, high conductivity electronic circuit board;
25% of the molybdenum-rhenium alloy is used for liquid rocket engine components and metal heat exchangers must be tough at room temperature.
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