Effect of Scanning Strategies on the Microstructure and Mechanical Properties of Ti-22Al-25Nb Alloy Fabricated through Selective Laser Melting

Abstract

In this study, Ti-22Al-25Nb intermetallic compound alloys are fabricated through selective laser melting (SLM) at four scanning speeds (600, 700, 800, and 900 mm/s). The microstructure and mechanical properties of the selective laser melting fabricated alloys are systematically evaluated. The results indicate that scanning speed significantly affects microstructure characteristics (e.g., relative density, grain size, texture density, and the precipitation of secondary phases). The variation laws of the relative density, grain size, and texture density are likewise affected by scanning speed. The relative density, grain size, and texture density increase and then decrease with the increase in scanning speed. The alloy fabricated with the lowest scanning speed (600 mm/s) exhibits the maximum relative density, grain size, and texture density. By contrast, the alloy with the highest scanning speed (900 mm/s) exhibits the minimum relative density, grain size, and texture density. Furthermore, the precipitations of the O phase and Ti3Al phase are primarily distributed in regions with a high strain concentration near the pool boundary. The alloy fabricated with a 600 mm/s scanning speed simultaneously achieves the highest strength and elongation, which is closely correlated with the uniform distribution of secondary phases.