High hardness in a nanocrystalline Mg97Y2Zn1 alloy

A nanocrystalline Mg97Y2Zn1 alloy was prepared with an average grain size of 21 nm by mechanical alloying of elemental powders. The structure of the alloy was characterized by X-ray diffraction and transmission electron microscopy. The hardness of the alloy as-milled for 8 h at room temperature was 2.1 GPa. After compaction and annealing at 573 K, the average grain size slightly increases to 28 nm with an increase in hardness to 2.4 GPa. These are the highest values for hardness yet reported for a crystalline Mg-based (>95% Mg) alloy. Possible factors leading to this high strength are discussed. (C) 2011 Elsevier B.V. All rights reserved.