Reactive mechanism and mechanical properties of in-situ hybrid nano-composites fabricated from an Al-Fe2O3 system by friction stir processing

In-situ Al/(Al13Fe4 + Al2O3) hybrid nano-composite was fabricated using reactive friction stir processing (FSP) by introduction of Fe2O3 powder into the stir zone of rolled AA1050 aluminum alloy. Composite reinforcements were produced in-situ by exothermic reaction of Al and Fe2O3 that initiated by hot working characteristics of FSP. However, the existence of intermediate phase (Fe3O4) suggests that the reaction was not completed due to short time of FSP. EBSD results showed that the matrix mean grain size decreased to 8 and 3 μm after FSP without and with introduction of powder, respectively; this was also associated with the marked increase in HAGB. The fabricated nano-composite exhibited superior hardness (45 HV) and ultimate tensile strength (~ 171 MPa) as compared to those of the base and FSPed alloy with no powder addition. Formation of in-situ reinforcements and grain refinement acted as major and minor contributors to enhancement of mechanical properties (hardness and ultimate tensile strength), respectively.