ZM3, ZM4 and ZM6 belong to Mg-RE-Zr alloys. Rare-earth elements can reduce the tendency of magnesium to oxidize in both liquid and solid states. Since most Mg-RE systems, such as the Mg-Ce "Mg-Nd and Mg-La binary phase diagrams are similar in magnesium-rich regions, that is, they all have simple eutectic reactions, they generally exist in the grain boundary. With a lower melting point eutectic.
These cocrystals, which exist on the grain boundary in the form of networks, are believed to act to suppress microscopic shrinkage.
Mg-RE-Zr alloys all have good casting properties, low porosity and low wall thickness sensitivities. ZM3, ZM4 and ZM6 alloys can all be repaired by nitrogen arc welding. The welding process performance is good, and the cutting process performance is similar to ZM5. The ZM6 alloy has been used in the manufacture of helicopter rear engine mounts, aircraft wing ribs, and hydraulic constant-speed device mounts, as well as rotor lead platens for 300,000-kilowatt turbine generators, and is widely used in the manufacture of various force members. ZM3 has been used in engine compressor casings, centrifuge cartridges and so on.
ZM4 has been applied to the hydraulic constant speed device housing. Due to the high damping capacity of this alloy, it can be used as a chassis and housing for instruments in radio engineering to reduce the harmful effects of vibration.
Like the rare earth metals often added to Mg-Zn alloys, the strength of the alloys is often increased in the Mg-RE alloys by adding Zn, and Zr is added to refine the grain structure of the alloys and play a role in the smelting process. The role of purification, in order to improve the corrosion resistance of magnesium alloys. For example, magnesium alloy EZ33 }v (RE) = 3%, di'Zn) = 2.5%, and two (Zr) = 0.6%), both with high strength, but also with high creep resistance, the use of temperature can be Up to 250cC. In Mg-RE, Mn is sometimes added because Mn has a certain solid-solution strengthening effect, at the same time, it reduces the diffusion ability of the atoms, improves the heat resistance, and has the effect of improving the corrosion resistance of the alloy.
Another important rare earth element in magnesium alloys is the maximum solubility of yo Y in Mg is 12.5%, and its solubility curve changes with temperature, indicating that it has a high tendency to age harden. Nd and Zr are often added to Mg-Y alloys. The Mg-Y-Nd-Zr alloy series has much higher room temperature strength and high temperature creep resistance than other alloys, and can be used up to 3000C. In addition, the corrosion resistance of Mg-Y-Nd-Zr after heat treatment is superior to all other magnesium alloys. Pure rare earth Y has certain difficulties in use, one of which is expensive, and the other is a high melting point (15,000) with high affinity for oxygen.
Mg-Th alloys also have excellent creep resistance, and the use temperature of forgings and castings can reach up to 3500C. Like RE, Th can also improve the casting and welding properties of magnesium alloys. The simplest Mg-Th alloys are Mg-Th-Zr ternary alloys, such as HK31 (w (`Fh) = 3%, w (Zr) = 0.7%), and their microstructure is somewhat similar to that of Mg-RE-Zr. Metaalloys, through proper heat treatment, Mg-Th compounds continuously precipitated in the grain can improve the room temperature mechanical properties of magnesium alloys, discontinuous Mg-Th dispersoids on the grain boundary can effectively inhibit grain boundary rotation at high temperatures. This improves its creep resistance. The addition of Zn to Mg-Th-Zr results in a further increase in creep resistance of the magnesium alloy due to the formation of acicular phases on the grain boundaries. Mg-Th alloys have been used on missiles and aircraft, but they are almost never used anymore because Th is a radioactive element that is harmful to human health.
security wall,also called Hesco Barrier.
Originally designed as to prevent dike will be eroded, and flood control, flood control, later to be used as a military fortress, which are widely used in military defense border guard military exercises special explosion-proof network, as the military equipment, used in combat troops in riot gear, temporary fort, prewar command, to replace the traditional manual trenches, can effectively block the attacks of guns and bullets.
it is connected by the spring with Welded Wire Mesh panels to form a cell. It can use a single cell, but also can be connected together to use. It is generally used with the geotechnical cloth.
Security Wall (Hesco Barrier)
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