UCLA

Single-crystal materials are indispensable for high-performance applications, yet their deployment remains constrained by conventional manufacturing techniques that depend on strict quasi-steady thermal conditions1. This requirement fundamentally conflicts with the intense cyclic thermal fluctuations inherent to additive manufacturing2, historically preventing the 3D printing of large or architected single crystals. Here we present a free-form additive manufacturing approach that resolves this contradiction by using delicately controlled alternating and pulsed heat inputs to govern and direct single-crystal growth. Using this method, we demonstrate the fabrication of metre-tall, centimetre-diameter single-crystal Ti-6Al-4V alongside, to our knowledge, the first single-crystal lattice structures containing complex zigzag ligaments, effectively eliminating theoretical size constraints for single-crystal components. The resulting bulk single-crystal Ti-6Al-4V exhibits an order-of-magnitude increase in creep resistance over standard grain-size scaling predictions, driven by the synergistic elimination of grain boundaries and an additive manufacturing-induced hierarchical α/β-architecture that regulates dislocation density, mobility and void evolution. Furthermore, we demonstrate the broad applicability of this technique by printing single crystals of hard-to-process refractory metals, including W, Mo, Nb and MoNb alloys. Our work introduces a large-scale method for single-crystal additive manufacturing, expanding the accessible materials library and enabling high-performance, complex geometries previously unattainable by classical methods.