Heat treatment for diecast parts supplies stronger castings

High pressure diecasting (HPDC) is one of the most cost-effective process for making large quantities of complex aluminum components in netshape. But while other cast aluminum parts can be heat treated to improve their mechanical properties, this had not been possible for many die castings.

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Australia's Commonwealth Scientific and Industrial Research Organization's (CSIRO) Light Metals Flagship has developed a new heat treatment process for strengthening aluminum HPDC parts.

Standard die castings contain trapped gas pores that expand, blister and distort the casting when conventional heat treatment is applied, making the parts unusable. Previous attempts to make them heat-treatable have focused on removing porosity from the cast parts. But Flagship researchers developed a process that did not depend on reducing porosity, and they successfully tested the technology on large batches of parts purchased from the industry.

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"Components treated with the new process do not show surface blistering or dimensional changes," said Roger Lumley, metallurgist for Light Metals Flagship. "They retain an as-cast appearance." The process doubles the strength of parts made from the common diecast aluminum alloys. The heat treated components exhibit fatigue resistance as high as some wrought aluminum products and thermal conductivity about 20% above the as-cast status, meaning that for engine or transmission applications, heat can be transferred or removed more efficiently and quickly. This could mean that HPDC parts would operate with lower amounts of fluid in cooling and lubrications systems.

The new heat treating process also may substantially raise energy absorption during fracture when heat treated for this purpose, which has significant implications for crash-sensitive structural components. For example, one common secondary alloy almost doubled in energy absorption when heat treated for that purpose. "We envisage that this will make it possible to use HPDC components more widely in load carrying structural and safety applications," Lumley said. The heat treating process is designed to be implemented in existing manufacturing facilities using conventional heat treatment equipment, such as continuous belt furnaces, fluidized beds or furnace systems designed specifically for rapid heat treatment.

After the success of the trials for HPDC parts up to 66 lbs. (30 kg), the Light Metals Flagships is looking for companies to collaborate on developing lightweight products through component design and implement the new procedures in the diecasting industry.

Visit http://www.csiro.au/ for more information.

"Heat treatment for diecast parts supplies stronger castings" The Free Library 01 March 2008. 20 May 2008 <http://www.thefreelibrary.com/Heat treatment for diecast parts supplies stronger castings.-a0177175205>.