Customized ASTM Magnesium Rare Earth Alloy Az91d Magnesium Alloy

Customized Magnesium Rare Earth Alloy High-Temperature Resistance And High Strength

Introduction:

Rare earth magnesium alloys generally refer to magnesium alloys containing rare earth elements.

The atomic size radius difference between most rare earth elements and magnesium is within ±15%, and they have a large solid solubility in magnesium, which has good solid solution strengthening and precipitation strengthening effects; it can effectively improve the alloy structure and microstructure, improve The mechanical properties of the alloy at room temperature and high temperature, and the corrosion resistance and heat resistance of the alloy are enhanced; the atomic diffusion ability of rare earth elements is poor, which has a significant effect on increasing the recrystallization temperature of magnesium alloys and slowing down the recrystallization process; rare earth elements also have good aging strengthening. It can precipitate very stable dispersed phase particles, which can greatly improve the high-temperature strength and creep resistance of magnesium alloys. Therefore, a series of rare earth-containing magnesium alloys have been developed in the field of magnesium alloys, so that they have high strength, heat resistance, corrosion resistance and other properties, which will effectively expand the application field of magnesium alloys.

Effect:

Melt purification
Rare earth elements have the functions of removing hydrogen, oxygen, sulfur, iron and inclusions in magnesium alloy melts, so as to achieve the effect of degassing refining and purifying melts.

Melt protection
Magnesium alloys are very easy to oxidize and burn during the smelting process. Industrial magnesium alloys are generally smelted by flux coverage or gas shielding, but there are many shortcomings. If the ignition temperature of the magnesium alloy melt itself can be increased, it is possible to achieve magnesium alloys. Direct smelting in the atmosphere is of great significance to the further promotion and application of magnesium alloys. Rare earth is a surface active element of magnesium alloy melt, which can form a dense composite oxide film on the melt surface, effectively prevent the contact between the melt and the atmosphere, and greatly improve the ignition temperature of magnesium alloy melt.

grain refinement
The enrichment of rare earth elements at the front of the solid-liquid interface causes the composition to be supercooled, and a new nucleation zone is formed in the supercooled area to form fine equiaxed crystals. In addition, the enrichment of rare earth elements prevents the growth of α-Mg grains. The grain refinement is further promoted. According to the Hall2Petch formula, the strength of the alloy increases with the refinement of the grain size, and the grain size has a greater impact on the strength of the hexagonal close-packed metal than the body-centered cubic and face-centered cubic crystals, so the grain refinement of magnesium alloys The resulting strengthening effect is extremely significant.

solid solution strengthening
Most rare earth elements have high solid solubility in magnesium. When rare earth elements are dissolved in the magnesium matrix, lattice distortion occurs in the magnesium matrix due to the difference in atomic radius and elastic modulus between rare earth elements and magnesium. The resulting stress will hinder dislocation motion, thereby strengthening the magnesium matrix. The role of rare earth element solid solution strengthening is mainly to slow down the diffusion rate of atoms and hinder the movement of dislocations, thereby strengthening the matrix and improving the strength and high temperature creep properties of the alloy.

diffusion enhancement
Rare earth and magnesium or other alloying elements form stable intermetallic compounds during the solidification of the alloy. These rare earth-containing intermetallic compounds generally have the characteristics of high melting point and high thermal stability. They are fine compound particles dispersed in grain boundaries and grain boundaries. At high temperature, the grain boundary can be pinned, the slip of the grain boundary can be suppressed, and the movement of dislocations can be hindered to strengthen the alloy matrix.

Aging Precipitation Strengthening
The higher solid solubility of rare earth elements in magnesium decreases with the decrease of temperature. When the single-phase solid solution at high temperature is rapidly cooled, an unstable supersaturated solid solution is formed. After a long time of aging, it forms fine and dispersed the precipitation phase. The interaction between the precipitates and dislocations increases the strength of the alloy.

Application:

Rare earth magnesium alloy has the characteristics of high temperature resistance and high strength. Due to the high cost of alloys after adding rare earth elements, in the past rare earth magnesium alloys were mainly used in aerospace, missile and other military industries, but with the development of society and economy, both military and civilian fields have been greatly expanded.

The rare earth magnesium alloy Mg Be RE has a high ignition point and can be widely used in coal mines, natural gas and parts that are easily in contact with combustible substances. In petrochemical industry, due to the high chemical stability of magnesium to fuels, mineral oils and alkalis, the developed flame-retardant and corrosion-resistant rare earth magnesium alloys can be used to manufacture, preserve and transport pipes, boxes and pipes for such liquids. storage tank. The good biocompatibility and non-toxicity of rare earth magnesium alloys are expected to be used as artificial bone materials to replace existing metal fixtures.

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