Small Angle Neutron Scattering Study on the Microstructural Evolution of Nano-Structured Ferritic Alloys with Different Mechanical Alloying Times

Two nanostructured ferritic alloys (NFAs) are produced in order to investigate the effect of the processing time of the mechanical alloying (MA) on the microstructural evolution and tensile properties. The microstructural evolution with the MA processing time is examined using small angle neutron scattering and transmission electron microscope analyses, which demonstrate that the number density of nanoclusters below 10 nm increases significantly and their mean diameter decreases as the MA time increases. The nano-sized particles are characterized using A-ratio calculations. The NFA sample mechanically alloyed for 120 hours reaches a high tensile strength of similar to 1320 MPa, while the NFA sample with a shorter MA time exhibits only similar to 800 MPa. The reason for the difference in the tensile strength is also discussed.