Synthesis, Microstructure, and Mechanical Behavior of Fe-Cu Composites

The synthesis, microstructure, and mechanical properties of ball-milled nanocrystalline (nc) Fe powder and immiscible Fe-Cu alloy composites are investigated in this thesis. Experimental approaches are described for the characterization of the grain size and hardness of nc Fe powders and the internal stress state of bulk Fe-Cu alloy composites are presented.

The grain size measurements of ball-milled Fe powders obtained from the XRD line broadening analysis (15 nm) and TEM observation (18 nm) showed good agreement between two results. From the nanoindentation tests, the hardness values of the ball-milled Fe powders were increased from 3.5 to 10.5 GPa as the milling time increased and the grain size decreased.

The mechanical behaviors of the coarse-grained (Regular) pure Fe, pure Cu, and Fe-Cu alloy compositeswere studied. The regular Fe-Cu alloy composites showed significantly higher tensile strengths than expected by a simple rule of mixture due to solid-solution strengthening effects, which were confirmed by SEM and nanoindentation tests. Finally, the intergranular strain evolution during tensile testing is investigated using the neutron in-situ loading measurements.