A scientist holding samples of high-pressure die-castings

Dr Roger Lumley holding three test castings: (left to right) as-cast; with conventional heat treatment; and heat-treated using the new CSIRO process.

Heat treatment of high-pressure die-castings

A CSIRO research team has developed a new heat-treatment process for strengthening aluminium components that should put manufacturers on the road to making lighter, more fuel-efficient vehicles.

  • 2 January 2008 | Updated 15 March 2013

High-pressure die-casting (HPDC) is the most cost-effective process for making large quantities of complex aluminium components in near to final form.

Typically, up to 20 small parts can be made every minute. 

Most are used in motor vehicles, but the process is also important for other industries.

While other cast and wrought aluminium alloy parts can be heat treated to improve their mechanical properties (such as strength, hardness, toughness, fatigue and ductility), this has not been possible until now for high-pressure die-castings. 

High-pressure die-castings contain trapped gas pores (porosity) which expand, blister and distort the casting when heat treatment is applied.  This makes the parts unusable.

Previous attempts at making them heat-treatable have tried to remove porosity from the cast parts, but these attempts have proved costly and time-consuming.

Current activities

Flagship researchers have developed a heat treatment process for conventional high-pressure die-castings that doesn’t depend on reducing the porosity yet eliminates blistering and results in improved material properties.

The aim is to develop an inline heat treatment system compatible with a die-casting cell. 

The new process may enable die-casters to make complex HPDC components using up to 30 per cent less alloy to achieve the same performance.

The new process may enable die-casters to make complex HPDC components, such as engine blocks and transmission housings, using up to 30 per cent less alloy to achieve the same performance. 

Apart from reducing manufacturing costs, the requirement for less metal will also reduce vehicle weight, leading to lower fuel consumption and lower greenhouse gas emissions.

The process will also allow more strength-critical, and more costly to produce, cast and wrought components to be substituted with much lower cost HPDC components in some applications.

The new process can also double the strength of HPDC parts made from the two aluminium alloys that account for more than 80 per cent of the world’s aluminium die-castings.

Outcomes

The team, lead by CSIRO's Dr Roger Lumley, has successfully trialled the technology on large batches of parts purchased from industry.

Dr Lumley’s team is looking to collaborate with industry to develop advanced lightweight products through component design as well as implement the new procedures in industry.

The Future Manufacturing Flagship has applied for an international patent for this technology.

A set of technical data sheets, providing test results after treatment with the process for a range of aluminium alloys under various tempering conditions are available at Technical data sheets for heat treated aluminium high pressure die castings.