Reaction Mechanisms in Al_2O_3/CuO Infiltration by Liquid Al

摘要

This work studies reactive mechanisms involved in liquid Al infiltration of green preforms containing tailored amounts of Al_2O_3 and CuO. Infiltration reactions involving Al and copper oxides are expected to produce Al_2O_3, as fine particulate reinforcements, and Cu, as Al-matrix strengthener. Preforms with 75 mol%-CuO were infiltrated with Al at 1000℃ and 1100℃ in air. Under low PO_2, copper oxides are reduced to Cu, blocking the opportunity for reactive infiltration. Also, the Al-Cu/Al_2O_3 contact angle is insufficiently low to drive spontaneous infiltration. At 1000℃, infiltration is incipient, indicating that CuO reaction with Al is not sufficiently vigorous to destabilize enveloping A1_2O_3. At 1100℃, CuO reduces to Cu_2O and infiltration is triggered, although the process is incomplete due to formation of a compact A1_2O_3 layer which inhibits metal supply to the reaction front. At or behind the halted infiltration front consumption of starting A1_2O_3 particles and formation of CuAlO_2 occur. The space among these phases is occupied by a Cu-rich matrix, rendering an almost totally densified micro-structure. This study shows that liquid Al infiltration of Al_2O_3/ CuO greens is possible at 1100℃, in air, due to destabilization of the Al_2O_3 enveloping film and reactive infiltration, promoted by the redox reaction between Al and copper oxide.