Heat treatment the road to lighter cars

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

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

The new CSIRO process will enable diecasters to make complex high-pressure diecast (HPDC) components – such as engine blocks, transmission housings and distributor housings – using up to 30% less alloy to achieve the same level of performance. Apart from reducing manufacturing costs, the requirement for less metal will also reduce vehicle weight, leading to lower fuel consumption and fewer greenhouse gas emissions.

The process will also allow more strength-critical – and more costly to produce – cast and wrought components to be substituted by HPDC ones.

High-pressure diecasting for high volumes
HPDC is the most cost-effective way of making the volumes of aluminium components with complex shapes found in all motor vehicles. In a typical casting operation, up to 20 small HPDC parts can be cast every minute. 

Heat treatment is applied to other cast and wrought aluminium alloy parts to strengthen the metal. However, HPDC parts are usually not heat-treated because of blistering and distortion, caused when gas bubbles trapped during casting expand on heating.

Diecasters have tried to come up with solutions aimed at removing porosity from the cast parts, but these have proved costly and time-consuming.

The CSIRO heat-treatment approach, however, does not involve changing the porosity resulting from conventional HPDC.

Trials show negligible blistering
The leader of the Light Metals Flagship project, Dr Roger Lumley of CSIRO's Manufacturing & Infrastructure Technology (CMIT), says CSIRO’s expertise in heat-treating aluminium alloys and advanced high-pressure diecasting has given it a competitive edge.

Dr Lumley led an earlier project to develop a series of novel aluminium alloy heat treatments (known as ‘T6IX’) that improve alloy strength and fracture toughness.

The new CSIRO process is predicted to double the strength of HPDC parts made from the two aluminium alloys from recycled material that account for more than 80% of the world’s aluminium diecastings.

“We’ve done trials on large batches of parts purchased from industry and developed treatments for those parts,” Dr Lumley says. "That has gone really well.

"In a recent batch of 575 parts, only one per cent of the parts blistered.”

Vision for the future
Dr Lumley’s team has applied for an international patent for the technology, and is seeking industry involvement to set up a treatment unit next to a HPDC cell to examine the feasibility of continuous inline treatment.

“Long-term, we hope to persuade car manufacturers to incorporate the improved properties and reduced weight into component design, and also consider replacing wrought or other cast parts with HPDC parts,” adds Dr Lumley.

Contact:
Roger Lumley, LMF Project Leader
Roger.Lumley@csiro.au 
       
Sam Tartaglia, Business Development Manager
Sam.Tartaglia@csiro.au
 

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In brief...

The Light Metals Flagship is a CSIRO initiative and part of the National Research Flagships program that aims to deliver scientific solutions to advance Australia's most important national objectives. One of the largest scientific initiatives ever mounted in Australia, it aligns closely with the Federal Government's National Research Priorities. The initiative brings together our national research resources to deliver breakthroughs in fields ranging from healthcare to light metals and the environment.

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