Research · Jack Aspinall

The group's research centres on magnesium, the lightest structural metal: alloy design and semi-solid processing. The goal is to build Britain's capability.

Thixomolding

Thixomolding processes magnesium in the semi-solid state: alloy granules are screw-fed through a heated barrel under argon, and shear breaks the solidifying dendrites into a thixotropic slurry that is injected into a steel die. The semi-solid metal fills the die less turbulently than the fully liquid metal in high pressure die casting, reducing porosity and giving finer, more uniform microstructures.

We are measuring the mechanical and corrosion properties of thixomolded alloys against their die-cast counterparts, to establish where the route improves performance and why.

Magnesium alloy design

Today's moulding alloys were designed for die casting, not semi-solid processing. We design alloys specifically for thixomolding, engineering the solidification path and processing window with thermodynamic modelling, using only abundant elements.

Why magnesium

Magnesium is the lightest structural metal: about a third lighter than aluminium and less than a quarter the density of steel. That makes it a route to lightweighting in cars, robotics, and aerospace, where lower mass means longer range, faster and more efficient motion, and lower fuel burn.

Solid-state batteries

By alloying lithium metal, we can change its properties, and therefore change its electrochemical performance. Understanding this, to enable rationally designed lithium alloys for high performance solid-state batteries, was the main focus of this research.

Lithium alloy electrodes

This work established how alloy composition and microstructure control the performance of lithium alloy negative electrodes, from lithium-rich magnesium alloys that improve contact retention on discharge, to two-phase alloys in which fast-diffusing intermetallics such as InLi and Li₃Bi provide continuous lithium transport pathways.

Interfaces and plating

Using operando scanning electron microscopy, we directly visualised how metallic interlayers lithiate and how lithium subsequently plates at the solid electrolyte interface, establishing design principles for controlled plating and interfacial stabilisation in anode-less cells.

Mechanics of lithium metal

Nanoindentation coupled with electron backscatter diffraction measured the elastic and plastic properties of lithium at the nanoscale, revealing a strong size effect in hardness that is relevant to lithium filament propagation through solid electrolytes.

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