Effect of Ca addition on interface formation in Al(Ca)/Al2O3 composites prepared by gas pressure assisted infiltration

The aim of the work is to study interface formation between Al2O3 particles and Al(Ca) matrix in dependence of Ca content. Aluminium matrix composites (AMC) subjected to investigation were prepared by gas pressure assisted infiltration of alumina beds with aluminium-calcium alloys. It is shown that alumina particles in the AMC are covered with a monocalcium aluminates layer whose coherence increases with increasing amounts of Ca in the aluminium-calcium alloys. Moreover, Al4Ca intermetallic phases are formed with increasing Ca content and interconnect alumina particles. XRD confirms the presence of both CaAl2O4 and CaAl4O7 ternary phases. However, HRTEM analysis confirmed CaAl2O4 with a rather complex structure containing a high density of stacking faults. It appeared that annealing at 735°C does improve consistency of interface for Al 2wt.%Ca/Al2O3 AMC, but do not affect the thickness of the interface in dependence on annealing time. [Display omitted] •Ca addition into Al matrix results in formation of ternary interfacial layer.•Increasing amount of Ca yields more compact interfacial reaction zones.•Formation of CaAl4O7 and CaAl2O4 was identified via XRD and HR-TEM.•Annealing yields formation of more consistent reaction zone.