In-situ generated particle synchronous enhancement of strength and toughness in pressureless sintered Ti3AlC2 layered ceramics

Abstract

Ti3AlC2 as a typical MAX phase has attracted extensive attention due to its advantages of both metals and ceramics. However, the decomposition of Ti3AlC2 during pressureless sintering leads to a low density, which restricts its application in complex-shaped components. To address this challenge, MgO, CeO2, Y2O3, and La2O3 were employed as additives to fabricate Ti3AlC2 ceramics with minimal decomposition via pressureless sintering. It was observed that these oxide additives reacted with aluminum and oxygen, forming MgAl2O4, CeAlO3, YAlO3, and LaAlO3, respectively. These in-situ generated aluminate particles effectively impeded the outward diffusion of aluminum and the inward diffusion of oxygen, thereby inhibiting the decomposition of Ti3AlC2. Furthermore, the thermal expansion mismatch between the in-situ generated particles and the matrix induced beneficial residual stresses. These combined effects contributed to the synchronized enhancement of both strength and toughness. Among the four additives, CeO2 displayed the best efficiency. Ti3AlC2-1.0 wt%CeO2 reached a flexural strength of 680.74 MPa and fracture toughness of 7.82 MPa m1/2, equivalent to those by pressure assisted sintering. The calculated toughness considering the residual stress was approximately 7.71 MPa m1/2, in good agreement with the measured value.