316L-toughened porous Al2O3-based ceramic functionally graded materials using binder jetting

Al2O3-based ceramic functionally graded materials (FGMs) containing 1 wt% CuO and 4 wt% TiO2 as sintering aids and 0–40 wt% 316L as a toughening phase are fabricated by binder jetting additive manufacturing, and the low-temperature co-sintering toughening mechanism was studied. According to the 3D Stereo Microscope and XRD results, the interfacial microstructure exhibited a noticeable gradient change after being sintered from 1200 °C to 1450 °C for 2 h, and the main phases were Al2O3, γ-austenitie, Fe3C and a small amount of δ-ferrite. The FGMs sintered at 1450 °C had maximum relative density, X–Z-axis dimensional shrinkage and average bending strength values of 70.05%, 4.89%, 10.15%, 17.53% and 26.9 ± 0.87 MPa, respectively. Bending cracks originated from the pure Al2O3-based ceramic layer and gradually propagated to the high-316L side, accompanied by the crack bridging and deflection phenomena. The maximum crack deflection degree was about 90° at 1200 °C and 1400 °C. Obviously, the existence of crack bridging and deflection illustrated that 316L addition effectively improves the toughness of FGMs.