Effect of Microstructural Scale on Thermal Shock Resistance of Aluminum‐Reinforced Alumina

Abstract

Thermal shock data are presented for two types of Al/Al 2 O 3 composites (35 vol% Al) with different microstructural scale and compared to a monolithic alumina. The fine‐scale Al/A1 2 O 3 material exhibits high room‐temperature strength (765 MPa) and a gradual decrease in retained strength with increasing quenching temperature difference, δ T , and improved thermal shock resistance—as compared to monolithic alumina—even at δ T = 600°C. The coarse‐scale Al/Al 2 O 3 composite shows high long‐crack fracture toughness (10.5 MPa·m 1/2 ) and almost no strength degradation up to δ T = 500°C. A qualitative picture for the effect of microstructural scale on thermal shock resistance emerges by employing a simple fracture mechanics description contrasting the crack driving force for transient stress fields with R ‐curve behavior.