Microstructure and mechanical properties of laser metal deposited Ti6Al4V alloy with near equiaxed β grain structure

Abstract

Ti6Al4V alloy produced by additive manufacturing are generally characterized by their columnar β grain structure and the resulting anisotropy in mechanical properties as a critical challenge in engineering applications. In the present work, a near equiaxed β grain structure is obtained in the Ti6Al4V alloy thin-wall specimens produced by laser metal deposition through tailoring laser power and interlayer dwell time. Microstructure, texture, and mechanical properties of the as-deposited alloys are investigated as functions of processing parameters. When the interlayer dwell time is fixed at 10 s, the columnar β grain structure changes to a near equiaxed morphology, and the grain width (size) decreases with increasing laser power from 1200 W to 1500 W. Recrystallization of the previously deposited layers during processing is suggested to be responsible for the formation of the near-equiaxed β grain structure. All the as-deposited alloys consist of a weakly textured α phase and the β phase at room temperature. The as-deposited alloys with the near-equiaxed β grains show superior mechanical properties, as evidenced by large elongation values up to 14%.