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.