No abstract

Tensile creep and creep rupture behaviors of alumindl7 vol% silicon carbide nanocomposite and monolithic alumina were investigated at 1200" to 1300°C and at 50 to 150 MPa. Compared to the monolithic alumina, the nanocomposite exhibited excellent creep resistance. The minimum creep rate of the nanocomposite was about three orders of magnitude lower and the creep life was 10 times longer than those of the monolith. The nanocomposite demonstrated transient creep until failure, while accelerated creep waS observed in the monolith. It was revealed that rotating and plunging of intergranular silicon carbide nanoparticles into the alumina matrix increased the creep resistance with grain boundary sliding.

This study focuses on interfacial bonding between intergranular silicon carbide particles and an alumina matrix, to determine the creep inhibition mechanism of alumina/ silicon carbide nanocomposites. It is revealed that the silicon carbide/alumina interface possesses much stronger bonding than the alumina/alumina interface through three approaches: investigation of fracture toughness and fracture mode and consideration of internal thermal stresses acting at grain boundaries, estimation of equilibrium thickness of intergranular glassy films by force balance, and direct observation of grain boundaries by TEM. The rigid bonding of alumina/silicon carbide interfaces causes inhibition of vacancy nucleation and annihilation at the interfaces, causing remarkably improved creep resistance of the nanocomposite.