Manufacturers in the transportation industry are always looking for ways to reduce vehicle weight, minimize fuel consumption and reduce exhaust emissions, so they continue to look at the use of aluminum alloys to help achieve these objectives. For example, reducing motor vehicle weight by 10% translates to a 5.5% decrease in fuel consumption and every two pounds in weight loss lowers CO2 emissions by 44 lb for a vehicle driven 105,000 miles. These kinds of benefits have R&D activities focusing on improving the properties of aluminum alloys and reducing processing costs to increase aluminum use in vehicles.
Heat treatable aluminum alloys gain strength by solution heat treating, quenching, and aging. The process is simple in concept, but process variations required to achieve final properties has made heat treating a professional specialty. Research is aimed at minimizing such specialization.
For example, the Center for Heat Treating Excellence (CHTE) at Worcester Polytechnic Institute's Metal Processing Institute is developing quantitative models to predict the response to solution heat treatment of cast and wrought aluminum alloys to eliminate extensive trial and error experimentation to develop solution heat treatment times and temperatures.
Fluidized bed technology is being developed to achieve rapid heat treatment through DOE's Office of Industrial Technologies NICE3 program that focuses on an in-line fluidized bed aluminum heat treatment system for cast components.
Purdue University is working to improve the uniformity of spray quenching of complex shaped aluminum alloy extrusions and castings. Also, NIST Advanced Technology Program is funding Technomics LLC (Plymouth, Minn.) to use a fluidized bed quenching system that uses a dry fluidized media instead of water or air to achieve the desired cooling while eliminating distortion encountered in eater cooling.
Also, commercial implementation of new aging practices has come with improved understanding of the precipitation hardening process. In the article on p 31, the Manufacturing and Infrastructure Technology Group at CSIRO in Australia describes a new aging process that offers the potential to improve the mechanical properties of aluminum alloys and reduce heat-treatment costs. The process involves aging for a short time at elevated temperature, after which alloys are quenched and allowed to undergo secondary aging at ambient or slightly higher temperatures. The technology can be applied to all aluminum alloys that respond to age hardening, and treatments can be tailored to improve specific properties.
The aluminum industry continues to stimulate important technological breakthroughs to promote the benefits of aluminum by examining both the fundamental understanding and practical implementation aspects of aluminum heat treating.