Temperature induced phase transformations and microstructural changes in nanostructured FeCu solid solutions using in situ neutron powder thermo-diffraction

摘要

In situ neutron powder thermo-diffraction experiments in the temperature range from 300 K to 1170 K have been carried out in nanostructured and metastable Fe_(15)Cu_(85) and Fe_(85)Cu_(15) solid solutions, which were synthesized by means of a mechanical alloying technique. We report on the microstructural changes and the phase transformations that take place during controlled heating and cooling processes. The average crystalline grain size is similar for both samples in the as-milled state (approx 16-20 nm) while the induced strain is 2.5 times higher in the Fe-rich powders, reaching 1 percent . Moreover, the alpha-gamma transformation for Fe_(15)Cu_(85) starts at temperatures lower (approx 900 K) than that expected for pure Fe (1183 K) due likely to the existence of local inhomogeneities in the composition of the ball milled material.