Porous nano-Al2O3/Fe–Cr–Ni composites fabricated by pressureless reactive sintering

Porous in situ nano-Al2O3 reinforced Fe–Cr–Ni metal matrix composites (MMCs) were fabricated from a mixture of Al/nano-Fe2O3/Cr/Ni powders via pressureless reactive sintering at 700–800 °C for 1–2 h. X-ray diffraction (XRD) demonstrated that the porous composites produced at 800 °C for 2 h consisted of Al2O3, Cr0.7Fe0.36Ni2.9 and Fe–Cr phases generally. Scanning electron microscopy (SEM) showed that the Al2O3 particles were ultrafine and uniformly distributed in the metal matrix. The pore sizes ranged from 1 μm to 20 μm for the sintered porous composites fabricated at 800 °C for 2 h. The resultant porous composite prepared under prepressing pressure of 200 MPa before sintering had more homogeneous and finer pore structure, lower porosity and higher bending strength and fracture toughness than those prepared under prepressing pressure of 5–100 MPa.