In situ fabrication of α-Al2O3 and Ni2Al3 reinforced aluminum matrix composites in an Al–Ni2O3 system

α-Al2O3 ceramic particles and Ni2Al3 intermetallic compound reinforced aluminum matrix composites were successfully fabricated via exothermic dispersion (XD) reaction in an Al–Ni2O3 system. Thermodynamic analysis indicated that the reaction between Al and Ni2O3 could occur spontaneously due to its negative Gibbs free energy. The reaction characteristic was discussed by using X-ray diffraction (XRD) method and differential scanning calorimetry (DSC) analysis. The results showed that the reactions of the Al–Ni2O3 system consisted of two steps as following: (1) the Al firstly reacted with Ni2O3 to form the stable α-Al2O3 particles and active Ni atoms; (2) the active Ni atoms further reacted with Al to form Ni2Al3. The values of activation energy of the two step reactions were around 457.3 and 282.4 kJ/mol, respectively. The scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) revealed that the Ni2Al3 blocks were uniformly distributed throughout the matrix, while the α-Al2O3 particles were slightly segregated in the matrix. The strength of the composite is controlled by the strength of Ni2Al3 phase, and the tensile strength and the elongation rate of the composite with 30 vol.% reinforcement volume fraction are 210 MPa and 8%, respectively.