This paper describes the thermal stability and microstructural evolution of nanocrystalline Fe_(92-x)Cr_8Hf_x alloyed powders containing 1 and 4 at.% Hf that were produced by high-energy mechanical attrition. The grain size and hardness were examined as a function of milling time at room temperature for durations between 0.5 and 20.0 hours. These same characteristics were also measured after annealing compacts and powders at temperatures ranging from 200 °C to 1000 °C for one hour. The hardness data shows a substantial increase up to approximately 5.0 hours milling time which indicates the mean grain-size has saturated, and then levels off for both compositions. Both compositions retained hardness values equal to or greater than the as-milled version of themselves during the annealing study up to approximately 800 °C.
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