A new bcc phase magnesium displays lightweight, strong, ductile, and thermally stable properties

Figure caption: X-ray diffraction patterns of the 5nm/5nm bcc/bcc and the 50nm/50nm hcp/bcc Mg/Nb nanocomposite, showing the entire bcc structure for Mg in 5nm/5nm samples. Copper was used as a pressure marker during these experiments.
Figure caption: X-ray diffraction patterns of the 5nm/5nm bcc/bcc and the 50nm/50nm hcp/bcc Mg/Nb nanocomposite, showing the entire bcc structure for Mg in 5nm/5nm samples. Copper was used as a pressure marker during these experiments.

Magnesium is the lightest structural metal, with 35% lighter than aluminum and 78% lighter than steel, thus possessing an exceptional lightweightness (strength-to-weight ratio). However, because of its hexagonal close packed (hcp) structure, the associated slips in hcp-Mg often causes Mg having limited ductility and formability. A research group has synthesized 5 nm/5 nm Mg/Nb nanocomposites that display exceptional strength, ductility, and thermal stability. Using the HPCAT facility, the group found that the Mg present in the 5 nm/5 nm Mg/Nb nanocomposite is of entirely body-centered cubic (bcc) structure, without any trace of hcp Mg.  The bcc nano-Mg leads to a 40% higher strength and 125% increase in strain to failure as compared to 50 nm/50 nm Mg/Nb nanocomposites (where Mg has an hcp structure) made by the same method. Thermal stability tests demonstrate further that despite the finer layer size, the bcc Mg/Nb nanocomposite has exceptionally high thermal stability. These results reveal an exciting potential for a new bcc phase of Mg to be lightweight, strong, ductile, and thermally stable, overcoming many of the bottlenecks with conventional hcp Mg. These findings reveal an alternative solution to obtaining lightweight metals critically needed for future energy efficiency and fuel savings. More in S. Pathak et al, Sci. Rep., 7, 8264, 2017.