Surface nanocrystallization of Mg-3 wt.% Li-6 wt.% Al alloy by surface mechanical attrition treatment

• Nanocrystalline surface layer was produced on Mg-3 wt.%Li-6 wt.%Al alloy by SMAT.
• Grain refinement induced by SMAT is dominated mainly by dislocation slip.
• Twinning is active at the early stage of grain refinement process.
• The hardness of the surface was enhanced by SMAT.

A nanocrystalline surface layer was produced on Mg-3 wt.% Li-6 wt.% Al alloy by means of surface mechanical attrition treatment (SMAT). Microstructure features of various sections were systematically characterized by transmission electron microscopy. The results indicate that grain refinement induced by SMAT is dominated mainly by dislocation slip. Twinning is active at the early stage of grain refinement process when the grain size is large. The dislocation-dominated deformation mechanism is attributed to the change of c/a ratio due to the alloying of Li in Mg matrix and the suppression of twinning due to grain refinement. Nanoindentation results show that the hardness of the surface is enhanced by SMAT.

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