Example 6
A sample alloy composition including a plurality of grains with a predetermined average grain size may be prepared according to the present prophetic example. Pure iron foil, for example, having a thickness of between about 1 μm to about 1 cm, is used as a precursor. The iron foil is heated at a temperature between about 650° C. and about 1600° C. for a period of time between about 0.5 hours and about 10 hours, followed by quenching in a liquid medium. The liquid medium includes cold water, brine, oil, liquid nitrogen, or liquid CO2. A grain structure associated with an average grain size between about 20 nm and about 100 nm is formed. The sample is nitrided using ammonia, at a temperature between about 120° C. and about 500° C., subject to a pressure between about 1 atmosphere and about 100 atmospheres. The nitride sample is annealed by a strained workpiece technique.
