(1) The strength and hardness of pure magnesium polycrystals are not high. Therefore, pure magnesium cannot be directly used as a structural material. Pure magnesium is usually used to prepare magnesium alloys and other alloys.
(2) Magnesium alloy is the green engineering material with the most development and application potential in the 21st century.
Magnesium can form alloys with aluminum, copper, zinc, zirconium, thorium and other metals. Compared with pure magnesium, this alloy has better mechanical properties and is a good structural material. Although wrought magnesium alloys have good comprehensive properties, magnesium is a close-packed hexagonal lattice, which is difficult to plastically process and has high processing costs. Therefore, the current amount of wrought magnesium alloys is much smaller than that of cast magnesium alloys. There are dozens of elements in the periodic table that can form alloys with magnesium. Magnesium and iron, beryllium, potassium, sodium, etc. cannot form alloys. Among the applied magnesium alloy strengthening elements, according to the influence of alloying elements on the mechanical properties of binary magnesium alloys, alloying elements can be divided into three categories:
1. The elements that improve strength are: Al, Zn, Ag, Ce, Ga, Ni, Cu, Th.
2. The elements that improve toughness are: Th, Ga, Zn, Ag, Ce, Ca, Al, Ni, Cu.
3. Elements that enhance toughness without much change in strength: Cd, Ti, and Li.
4. Elements that significantly increase strength and decrease toughness: Sn, Pd, Bi, Sb.
The influence of impurity elements in magnesium
A. Most of the impurities contained in magnesium have adverse effects on the mechanical properties of magnesium.
B. When MgO exceeds 0.1%, the mechanical properties of magnesium will be reduced.
When the content of C and Na exceeds 0.01% or the content of K exceeds 0.03, the tensile strength and other mechanical properties of magnesium will also be greatly reduced.
D. But when both the Na content reaches 0.07% and the K content reaches 0.01%, the strength of magnesium does not decrease, but only its plasticity.
The corrosion resistance of high-purity magnesium alloy is equivalent to that of aluminum
1. Magnesium alloy matrix is close-packed hexagonal lattice, magnesium is more active, and oxide film is loose, so its casting, plastic deformation and anti-corrosion process are more complicated than aluminum alloy.
2. The corrosion resistance of high-purity magnesium alloys is equivalent to or even lower than that of aluminum alloys. Therefore, the industrial production of high-purity magnesium alloys is an urgent problem to be solved in the mass application of magnesium alloys.
Post time: Dec-06-2021