Magnesium-lithium alloy

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Magnesium-lithium alloys are magnesium alloys that have improved properties through the addition of lithium . In particular, the poor ductility of pure magnesium and most magnesium alloys is improved by the addition of lithium. In addition, Mg-Li alloys are ideal for lightweight construction, as very low densities (up to 1.3 g / cm³) with high rigidity at the same time can be achieved. So far, they have mainly been used in the aerospace and defense industries. The low corrosion resistance and high tendency to oxidize in the molten state represent further massive application inhibitors.

Addition of up to 17% lithium

In the hexagonal atomic lattice of magnesium, crystallographic sliding takes place at temperatures below 220 ° C only within the basal plane. As a result, no plastic deformation with elongation of the cylinder axis can be realized in this temperature range, which leads to a low elongation at break. By adding 4 percent by weight of lithium, the prismatic sliding systems can be activated, through which sliding on the lateral surfaces of the hexagonal unit cell is possible. For example, the alloy MgLi12Al3 shows a strength comparable to that of the commercially available magnesium alloy AM20 with better ductility.

Addition of 17 to 30 at% lithium

If more than 17 at% (atomic percent) lithium is added, a two-phase structure consisting of body-centered cubic lithium crystal and hexagonal magnesium crystal results .

Addition of more than 30 at% lithium

At more than 30 at%, the magnesium atoms are dissolved in the lithium lattice. Pure Mg-Li alloys have no technical application due to their low load capacity. Aluminum is often used as an additional alloy element . For example, the alloy MgLi40Al3 has a moderate strength, a low density (high mass-related strength), good castability and good ductility, and can be easily machined.

See also

Individual evidence

  1. ↑ Plane-Strain compression of Magnesium and Magnesium Alloy Crystals, EW Kelley and WF Hosford Jr., Transactions of the Metallurgical Society of AIME, Vol. 242, 1968, pp. 5-13.
  2. ^ Magnesium-lithium alloys, H. Haferkamp and Jaschik, C., in: Magnesium Taschenbuch, ISBN 3-87017-264-9 .