The solid-state combustion synthesis of in-situ hybrid (Al₃Ni+Al₂O₃)/Al composites and evaluation of its mechanical properties

In-situ hybrid (Al3Ni+Al2O3)/Al composites with bimodal size particles distributions were fabricated via an Al-NiO solid-state combustion reaction and subsequent hot extrusion process. The reaction system between Al and NiO was investigated by differential thermal analysis (DTA). The presence of Al2O3 and Al3Ni in the matrix was verified by XRD/EDS analysis. The in-situ formed Al3Ni phase with varying morphologies and sizes such as particle, plate, strip and flake at different sintering temperatures were observed. And the exothermic reaction of Al-NiO can be reduced to below the melting point of Al, and the desirable sintering temperature was. 600 celcius. In hot-extruded samples, both nano Al2O3 and Al3Ni particles distributed homogeneously, and most of Al3Ni particles is smaller than 2 mu m in size. When NiO content increases from 8% to 12%, Al matrix grains in composites can be refined from 1.7510 mu m to 1.2050 mu m. The mechanical properties of composites are enhanced significantly due to the introduction of Al3Ni and Al2O3 particles, and can be up a YS of 322 MPa and a UTS of 407 MPa in the 15% NiO-Al composite. In addition, when the content of NiO increases from 10% to 12%, the strength of composites enhances without obvious sacrifice of EI. The strengthening and toughening mechanisms also was discussed in detail.