Dispersion Strengthened Magnesium Alloys - Solidification of Nanocolloids

Vehicle lightweighting represents a vital strand of an integrated national approach to transport decarbonisation. There is a general agreement that the CO2 emissions from cars needs to be cut by at least 50% to prevent the well-to-wheels carbon emission from the world car fleet rising above 7bn tonnes rather than the more sustainable 4bn tonnes by 2050. The UK Government has set an even higher target of a 60% reduction in transport sector CO2 emissions by 2030. Implementation of lightweighting across all classes of vehicles plays an important role in achieving this target.

Magnesium (Mg), as a lightest structural metal combined with superior damping capacity, has tremendous potential in achieving lightweighting in vehicles with improved noise, vibration and harshness performance. Recent Mg market research suggests that the global Mg alloys market will increase from £1 billion in 2018 to £2.8 billion by 2026, at a CAGR of ~12.7% between 2019 and 2026 which is expected to be driven by demand for Mg alloys from the automotive & transportation applications due to fuel efficiency and emission regulations. The automotive industry is aiming to increase Mg content from 8.6kg/car in 2017 to 45kg/car by 2030. Among variety of Mg alloys, aluminium containing Mg (Mg-Al) alloys are being used in automotive sector due to their competitive cost. However, their widespread use in vehicle is hindered by their lower strength. To help realise this growth and to meet the stringent design and safety criteria for lightweighting, it is necessary to enhance the strength of existing cost-effective Mg-Al alloys significantly.

The addition of rare-earth (RE) elements and noble metals in magnesium has been successfully utilised to achieve a significant improvement in strength. The alloys that have high RE content exhibit improved strength that meets lightweight design requirement. However, due to the resource scarcity and high cost, the alloys containing RE elements are impractical for their mass structural applications in automotive sector. The role of precipitation hardening in Mg alloys could be fulfilled by ex-situ phase particles, if they are dispersed within the Mg matrix rather than segregated at the grain boundaries. Substantiated by the proof-of-concept study, the proposed research programme aims to develop high strength, cost effective dispersion strengthened magnesium (DSM) alloys. It also investigates the criteria for the stability of nanocolloids, solidification behaviour and establishes process maps suitable for manufacturing DSM alloys using practical casting processes.

Technologically, the DSM alloys represent a step change in the manufacturing technology to produce lightweight automotive components. If certain Al and steel are replaced with DSM alloys, the expected weight saving would be significant. In the longer term, it will lead to a significant reduction in CO2 emissions and offer sizable fuel savings. The industrial partners, comprising a materials supplier, component producers, alloy designer and an end user are an added value and help to accelerate the knowledge transfer activity from academia to industry.