Metastable Alloys
If thermodynamics could be summarized in one word, that word would be "equilibrium." Thermodynamics portrays processes accurately only under equilibrium conditions. Fortunately, Mother Nature is not that strict, so all the equations we've learned work well under most conditions. Often, it's useful to turn this restriction around and purposely introduce a non-equilibrium condition to generate an unusual, metastable material. Honeywell did this many years ago when it produced Metglas, an amorphous metal with many unique properties. It was formed by rapidly quenching a molten metal on a rapidly spinning cooled wheel. The cooling rate is nearly a million degrees per second, and the process is aided by using alloy compositions with deep eutectics. Materials scientists at Sandia National Laboratories are investigating a more extreme process for producing metastable alloys. They are using intense radiation to produce superalloy nanoparticles from precursor solutions [1].
The Sandia team, led by Tina Nenoff, is investigating this unique method for production of superalloy nanoparticles to improve weapons casings and gas turbine engines. Superalloys, as their name implies, have excellent oxidation and corrosion resistance, and they have strength at high temperature. Development of improved superalloys has followed the traditional path of changing the proportions of the alloyed elements, adding additional elements, and changing temperature treatment conditions. The Sandia work takes the novel approach of using intense electron and proton irradiation to decompose precursor molecules and grow nanoparticles of metal alloys in an alcohol solution. The process is called "radiolysis." The process allows the creation of metastable alloy phases that can't be prepared by the typical melting/solidification/heat-treatment process. The Sandia process produces particles that are of uniform size and defect-free. The particles themselves are not radioactive.
Reference:
1. Darrick Hurst, "Nanoparticles unlock the future of superalloy metals" (Sandia Press Release, June 13, 2007).