Ti2AlC bulk ceramics produced by gelcasting and Al-rich pressureless sintering

Abstract

Ti2AlC bulk ceramic was produced via aqueous gelcasting followed by Al-rich pressureless sintering. The processing parameters were optimized and two pressureless sintering methods of Al-rich and C-rich were compared and analyzed.The results showed that stable Ti2AlC slurry and homogeneous green body can be obtained at the pH value, zeta potential, dispersant content and solid content of 10, 65.2 mV, 1.6 wt%, and 48 vol%, respectively. Impurities of 0.6 ppm O2 and 0.2 ppm N2 containing in the flowing argon promoted the thermal dissociation of the gelcasted bulk Ti2AlC, forming whiskers of Al2OC and cloud-like floccule of AlN and simultaneously resulting in the delamination of a duplex layer, an outer ring layer of Ti3AlC2 and a loose and porous cracking layer of Ti2AlC–Ti3AlC2. The synergistic effect of the porous reaction layer and the unclosed channels formed after debinding resulted in a severe decrease in the density and mechanical properties of the C-rich pressureless sintered samples. In contrast, the Al-rich pressureless sintering system can provide a strong and effective protection for the sintering of the gelcasted Ti2AlC green body. The density, hardness, flexural strength and fracture toughness of AlRC sample reached 3.98 g/cm3, 4.29 GPa, 341 MPa, 4.83 MPa m1/2, respectively.