The Effect of Indium Additions on Mg-Li and Mg-Li-Al Alloys

It is known that BCC Mg-Li alloys offer the opportunity to realize both high specific strength and good ductility in a light weight alloy. The commonest addition to this system is Al due to its solid solution-strengthening ability. This system is also known to precipitate a potent metastable phase that subsequently transitions to the equilibrium AlLi phase. There are other systems, Zn, Cd, and In, which are also known to precipitate a phase that is similar to the AlLi phase. Of these additions, the phase-evolution characteristics associated with adding In to Mg-Li and Mg-Li-Al alloys are largely unknown. This article seeks to understand the phase transformation, microstructural evolution, and mechanical behavior of In additions by systematically studying Mg-Li-In in contrast to Mg-Li-Al and Mg-Li-Al-In. This study represents an initial investigation of the Mg-Li-In system, while simultaneously determining Indium's potential as a microalloying addition. It was found that in the compositional ranges under investigation, a metastable phase does form in each system, and at longer aging times, In3Li13 is found to precipitate. Commentary and insight are also provided with respect to precipitate nucleation and coarsening behavior. (C) The Minerals, Metals & Materials Society and ASM International 2013