![Figure 1. Specific strength vs. elongation to failure for a range of Mg alloys. Red diamond: LX41; blue square: Mg-30Li; further symbols correspond to literature data for other hot-rolled Mg alloys and are explained in the original publication [Y. Estrin et al., Materials Letters 173, 252–256 (2016), doi:10.1016/j.matlet.2016.03.052].](//assets.materialstoday.com/wpimg/float/b6198d64-92fe-440b-8609-dc52c30023d0.jpg)
Figure 1. Specific strength vs. elongation to failure for a range of Mg alloys. Red diamond: LX41; blue square: Mg-30Li; further symbols correspond to literature data for other hot-rolled Mg alloys and are explained in the original publication [Y. Estrin et al., Materials Letters 173, 252–256 (2016), doi:10.1016/j.matlet.2016.03.052].In a quest for ultra-light alloys for modern engineering materials, researchers are turning their attention to alloying the lightest available structural metal, magnesium, with even lighter element, lithium. The well publicized success of Mg-30 at. % Li alloy reported recently by a team of researchers from Australia and China [W. Xu et al., Nature Materials 14, 1229–1235 (2015), doi:10.1038/nmat4435] has raised the hopes that alloys of the Mg-Li system with exceptional combinations of strength, ductility, and corrosion resistance can be developed for commercial use.
A particular range of applications for which Mg alloys are considered as viable candidate materials is in medical implants, including vascular stents and implants for bone replacement. The high Li content of the mentioned alloy precludes its use for such applications. However, alloys with a lower level of Li, such as LAE442 that contains 4 wt. % Li, were shown [F. Witte et al., Acta Biomaterialia 6, 1792–1799 (2010), doi:10.1016/j.actbio.2009.10.012] to exhibit low corrosion rates and acceptable host response in vivo.
An international group of researchers based in Australia, Russia, India, and Germany has now developed a Mg-based alloy with a similar level of Li that in addition contains 1 wt. % Ca [S.S. Nene et al., Journal of Alloys Compounds 615 501-506 (2014), doi:10.1016/j.jallcom.2014.06.151].
In a most recent article [Y. Estrin et al., Materials Letters 173, 252–256 (2016), doi:10.1016/j.matlet.2016.03.052], it was reported that after hot rolling at two different temperature levels (two-step rolling, TSR) and subsequent 30 min annealing (TA30), the alloy Mg-4Li-1Ca (LX41) exhibits an exceptional property profile. As seen from Fig. 1, LX41 is almost on par with the Mg-30Li alloy in terms of room temperature ductility (as represented by the elongation to failure) and slightly outperforms it in specific strength, i.e. the strength to density ratio. It is also evident from Fig. 1 that LX41 in the TA30 condition is superior to other hot rolled Mg alloys.
The authors relate these superior properties to microstructure and texture of the alloy after it has been processed in the way proposed. What is of particular significance is a reasonably good cytocompatibility of the new alloy, which gives promise for its suitability for medical implants.
An outcome of this work important in terms of possible adoption of LX41 alloy by industry is the demonstration that it can acquire a range of excellent properties by means of readily available processing techniques. The processing schedule involves conventional hot rolling to just 60% of thickness reduction at two significantly lower temperature levels and subsequent annealing treatment. This gives reasons to believe that the new alloy has the potential to become a game-changer in the race for developing ultra-light Mg alloys.