• Optimal alumina fiber addition of 0.6wt.% yields the best comprehensive performance of ceramic shell molds, with high room- and high-temperature strengths and minimal self-weight deformation.
• Green bending strength peaks at 6.20 MPa with 0.2wt.% alumina fibers, but further additions do not significantly enhance it.
• High-temperature strength and resistance to self-weight deformation first increase then decrease with fiber content, peaking at 0.6wt.%.
• Fiber reinforcement mechanisms such as bridging and pulling-out consume crack growth energy, improving shell mold strength.