Researchers at the Department of Materials Engineering (MatE), Indian Institute of Science (IISc) and collaborators have developed a new lightweight cast aluminium alloy that is both exceptionally strong and remarkably ductile, overcoming one of the biggest challenges in the structural metallurgy of aluminium alloys.
The new alloy exhibits about 400% improvement in ductility and 50% higher strength than conventional aluminium eutectic alloys. Importantly, it retains high mechanical strength even at 250°C, making it a promising material for aerospace, automotive, and energy applications that require components to withstand demanding mechanical and thermal conditions. The study was published in Nature Communications.
Cast aluminium alloys are widely used because they are lightweight and inexpensive to manufacture. However, they often fail prematurely because microscopic brittle fibres embedded in the alloy act as crack initiation sites. Once loaded, these brittle regions fracture easily, limiting the alloy’s ductility and structural reliability.
The IISc team solved this long-standing problem by tweaking material design at the atomic scale. By introducing a minute amount of zirconium into an aluminium-gadolinium alloy and applying controlled heat treatment, the researchers discovered the formation of an ultrathin superlattice nano-layer surrounding the brittle fibres. This ordered atomic layer strengthened the interface between the brittle fibres and the soft aluminium matrix, preventing cracks from initiating and allowing stresses to be transferred much more efficiently.
“Discovering the superlattice nano-layer was one of the most exciting moments of my PhD, as it revealed a completely new interface-strengthening mechanism that enables aluminium alloys to become stronger and more ductile,” says Hemant Kumar, first author and PhD student at MatE.
In addition to the nano-layered fibres, the alloy also developed billions of core-shell nanoparticles dispersed throughout the aluminium matrix. These nanoparticles promote the formation of extremely fine dislocation networks during deformation, enabling the material to accommodate much larger plastic strains before failure.
Using state-of-the-art microscopy and characterisation techniques available at the Advanced Facility for Microscopy and Microanalysis (AFMM), IISc, the researchers directly visualised the atomic arrangement of these new nanostructures and revealed how they fundamentally alter deformation mechanisms within the alloy.
Beyond enhanced properties at room temperature, the alloy maintains excellent strength and creep resistance even at elevated temperatures. Its properties make it attractive for replacing heavy materials in aerospace and automobile components, which can significantly improve fuel efficiency and reduce greenhouse gas emissions, according to the researchers.
“This discovery represents a first-of-its-kind breakthrough in metallurgy from India. By engineering interfaces atom-by-atom, we have demonstrated a fundamentally new strategy for designing lightweight, high-temperature aluminium alloys with an exceptional combination of strength and ductility,” says Surendra Kumar Makineni, Associate Professor at MatE and corresponding author of the study. “We believe that this concept opens new avenues for developing next-generation structural materials for aerospace, automotive, and energy applications.”
-Rashmi Kumari
