Effect of metallic phase content on mechanical properties of (85Cu-15Ni)/(10NiO-NiFe2O4) cermet inert anode for aluminum electrolysis
(School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China )
Abstract: (85Cu-15Ni)/(10NiO-NiFe2O4) cermets were prepared with Cu-Ni mixed powders as toughening metallic phase and 10NiO-NiFe2O4 as ceramic matrix. The phase composition, microstructure of composite and the effect of metallic phase content on bending strength, hardness, fracture toughness and thermal shock resistance were studied. X-ray diffraction analysis indicates the coexistence of (Cu-Ni), NiO and NiFe2O4 phases in the cermets. Within the content range of metallic phase from 0% to 20% (mass fraction), the maximal bending strength (176.4 MPa) and the minimal porosity (3.9%) of composite appear at the metallic phase content of 5%. The fracture toughness increases and Vickers’ hardness decreases with increasing metal content. When the thermal shock temperature difference (∆t) is below 200 ℃, the loss rate of residual strength for 10NiO-NiFe2O4 ceramic is only 8%, but about 40% for (85Cu-15Ni)/(10NiO-NiFe2O4) cermets. As ∆t is above 200 ℃, the residual strength sharply decreases for sample CN0 and falls slowly for samples CN5−CN20.
Key words: NiFe2O4; cermet inert anode; aluminum electrolysis; metallic phase; fracture toughness; thermal shock resistance