“Broadly speaking, heat treatment involves the controlled heating and cooling of a product, in a specific way, to change its microstructure,” ALFED

ALFED, the Aluminium Federation, collaborates with businesses and stakeholders to foster innovation, promote best practices and champion the industry’s interests. As the voice of the UK industry, its mission is to expand the market for aluminium products by helping members solve problems, lobby government and boost their competitiveness.

AL Circle: Can you describe the importance of heat treatment in the aluminium industry and its role in enhancing the properties of aluminium products?

ALFED: Aluminium is one of the two most common materials that undergo heat treatment, where it's used to alter the physical and chemical properties of the material. The versatile process can be used to improve the hardness, change the colour and alter the ductility of a material.

Each aluminium alloy has unique properties that make it suitable for specific applications, and heat treatment allows manufacturers and producers to refine those properties further. However, not all aluminium alloys can be treated - it all depends on the chemical composition of the alloy.

AL Circle: What are the key heat treatment processes commonly used in the aluminium industry, and how do they differ?

ALFED: Broadly speaking, heat treatment involves the controlled heating and cooling of a product, in a specific way, to change its microstructure.  Four of the most commonly used treatments for aluminium, include annealing, solution heat, natural and artificial aging and homogenising.

• Annealing - This process sees the material heated to a high temperature and then allowed to cool slowly. Alongside reducing stresses in the material, it also improving its machinability and making it more ductile and soft. It is commonly used on aluminium parts that are forged, extruded or cast.
• Solution heat - Also known as quenching, this treatment involves a similar heating process to annealing, but the material is quenched, typically in water, before being cooled. This maximises the concentration of the hardening alloying elements, but can make the material more brittle.
• Natural Aging - This process gradually strengthens and hardens the alloy to a greater level than initially present and can be achieved naturally or artificially. With natural aging, most of the hardening occurs during the first 24 hours of the treatment, but reaches full effectiveness after five days. Artificial aging is required when the alloy is unable to reach its maximum strength by natural aging alone due to its components. These alloys benefit from further heating at a much lower temperature, typically for between 6 and 24 hours, before cooling to room temperature.
• Homogenising - Undertaken at a much higher temperature than annealing, this process heats an alloy to just below its critical point before cooling slowly. This allows elements with lower melting temperatures (such as pure aluminium) to solidify on the outside edges first and elements with a higher melting temperature to migrate and concentrate in the centre of the castings walls.

Alongside the type of alloy and the parameters of the heat treatment used, the suitability of heat treatments for products also depends on its final application and the manufacturing process it will withstand.

AL Circle: How do you see the future of heat treatment in the aluminium industry evolving, particularly in terms of adopting sustainable practices and reducing environmental impact?

ALFED: With continuous R&D and investment, the landscape for a more sustainable future is ever-growing. There are a number of businesses across the supply chain innovating within heat treatment to improve its sustainability.

For example, some are beginning to utilise the concept of heat treatment thermal loop solutions. While offering several advantages over traditional methods, such as improved temperature control and increased efficiency, it also provides several sustainability benefits. From smaller energy consumption to reduced waste, this efficient solution reduces the environmental impact of heat treatment processes.

AL Circle: Are there any emerging trends or technologies likely to shape the future of aluminium heat treatment?

ALFED: There are a number of emerging trends and technologies that will have a significant impact on the future of aluminium heat treatment in some way – to what extent; we’ll have to see as they unfold.

For us, the sustainable development of the process should be an aspect we’re all taking an interest in. Heat treatment has the ability to contribute to a more sustainable future by improving the efficiency, quality and durability of the metal products and applications, while also adopting more environmentally friendly practices, such as using renewable energy sources, recycling and reusing materials, reducing emissions and wastes and minimising hazards and risks.

Then, there are the less common advances including:

• Additive manufacturing - where new models and methods are being developed to optimise the heat treatment parameters of additive manufactured metals and alloys.
• Smart materials - with heat treatment playing a significant role in designing and producing smart materials as it affects the phase transformation, structure and defect formation of the materials.
• Nanostructured materials - where heat treatment is important for controlling the formation, stability and performance of nanostructured materials, as it influences grain size, grain boundary, phase composition and defect distribution.

Computational modelling – this tool can be applied to various aspects of the heat treatment process to provide a comprehensive and realistic representation of heat treatments and the outcomes on specific materials.