Optimization of Post-processing Annealing Conditions of the Laser Powder Bed-Fused Ti–18Zr–14Nb Shape Memory Alloy: Structure and Functional Properties

Abstract

Ti–18Zr–14Nb (at%) shape memory alloy was processed by laser powder bed fusion (LPBF) and subjected to post-processing annealing treatments in the 500–800 °C temperature range. The microstructure, crystallographic texture, static mechanical properties, and low-cycle fatigue behavior of this alloy in the as-built state and after different post-fusion annealings have been studied. It was found that a strongly columnar microstructure developed during LPBF processing morphed into a predominantly equiaxed grain structure after 800 °C recrystallization annealing. However, the highest number of cycles to failure during high-intensity strain-controlled fatigue testing (2% of strain in a cycle) was obtained after annealing at 500 °C, whereas the lowest number of cycles was found after annealing at 700 °C. A beneficial combination of static and fatigue mechanical properties with a relatively low Young’s modulus makes 500 °C-annealed LPBF Ti–18Zr–14Nb components suitable for biomedical applications, especially where the capacity of LPBF to manufacture geometrically complex and patient-specific load-bearing components makes a difference.