Beyond Wire and Tube: Sinter-Based Additive Manufacturing of NiTi Shape Memory Alloys via Lithography-Based Metal Manufacturing

Abstract

This article introduces lithography-based metal manufacturing (LMM), a sinter-based additive process for nickel-titanium (NiTi) shape memory alloys that overcomes the geometric limitations of conventional wire-drawing, tube-laser-cutting, and billet-machining routes while preserving the alloy's critical Ni:Ti chemistry by avoiding melting. The process achieves high density (98.6–99.7%) and, after heat treatment, yields mechanical properties that meet ASTM F2516 superelastic criteria, with tunable transformation temperatures, though interstitial carbon and oxygen levels currently exceed ASTM F2063 wrought-material limits. Two promising application fields are examined: minimally invasive delivery instruments, where geometric consolidation eliminates joints and assembly steps, and orthopedic bone-contacting implants, which benefit from porous, patient-specific NiTi geometry.