What is The Role of Rare Earth and Other Additive Elements in Magnesium Alloys?>

Aluminium(Al)--increases the room temperature strength of the alloy and gives the heat treatment strengthening effect.

Zinc(Zn)-- can improve the strength, plasticity and creep resistance of alloys. Zinc content greater than 2.5% has a negative impact on the corrosion resistance of the alloy. The general content is controlled below 2%.

Manganese(Mn)-- has little effect on the mechanical properties of the alloy, but reduces the plasticity. The main purpose of adding 1% to 2.5% Mn to magnesium alloys is to improve the stress corrosion resistance of the alloys, thereby improving the corrosion resistance and the welding properties of the alloys.

Silicon(Si) - can be used to improve the thermal stability and creep resistance of die castings.

Zirconium(Zr) - can refine grains, reduce the tendency of hot cracking, improve mechanical properties and improve corrosion resistance. Adding 0.5% to 0.8% Zr to magnesium alloy has the best grain refinement effect.

Calcium(Ca) - can refine the structure, improve the creep resistance, and further reduce the cost.

Rare earth elements - can significantly improve the heat resistance of magnesium alloys, refine grains, reduce microporosity and hot cracking tendency, and improve casting properties and welding properties. Generally not prone to stress corrosion. Commonly used rare earth elements are Ce, La, Nd, Pr and Y, Gd,etc.

Impurity elements Fe, Ni, Cu, Co—these four elements have very small solid solubility in magnesium, and when their concentration (mass fraction) is less than 0.2%, they will have a harmful effect on Mg and accelerate the corrosion of magnesium alloys.

Rare earth elements play a very important role in magnesium alloys and have a great impact on the performance and formability of magnesium alloys. Rare earth elements can purify the alloy solution, improve the alloy structure, improve the mechanical properties of the alloy at room temperature and high temperature, and enhance the corrosion resistance of the alloy.

Rare earth metals have strong chemical activity, can remove H, O, S, Cl, Fe and other inclusion elements, and can improve the fluidity and processing performance of alloys. . Rare earth can change Fe, Co, Ni, and Cu in the solute state in the alloy to the state of Mg-Re-Fe(Cu)-Al (or Zn.Mn) intermetallic compound, and inhibit the corrosion effect of iron on the alloy.

The rare earth-containing magnesium alloy can form a passive film in solution to improve its corrosion resistance. The addition of rare earth to magnesium alloys can refine the alloy structure, promote the transformation of the oxide film on the surface of the alloy from loose to dense, reduce the oxidation tendency of the alloy in liquid and solid state, and improve the heat resistance and corrosion resistance of the alloy.

It is generally believed that trivalent rare earth elements increase the electron concentration in the alloy, increase the atomic bonding force of the magnesium alloy, and reduce the atomic diffusion rate of magnesium at 200~300 °C, especially the compound of magnesium and rare earth has high thermal stability and can improve the Thermal stability of alloys.

Rare earth elements have a large solid solubility in magnesium, which can achieve solid solution strengthening and precipitation strengthening; rare earth elements form intermetallic compounds with high melting point and good thermal stability with Mg, Al and other alloying elements such as (Zn, Zr, Mn) To achieve dispersion strengthening, thereby improving heat resistance, high temperature creep resistance and other properties. The higher creep properties of rare earth-containing magnesium alloys are mainly attributed to the dispersion strengthening of Mg-Re compounds and their effects on grain boundary sliding.