Investigating crystallographic parameters and their impact on mechanical properties of Ti6Al4V alloy from selective Laser melting

Abstract

Selective Laser Melting (SLM) is a highly adaptable additive manufacturing method notable for its feature accuracy and flexibility. Processing Ti-6Al-4V alloy using SLM is particularly advantageous because of the alloy's unique structural features and thermal characteristics, making it well-suited for demanding applications where lightweight design, strength, and durability are essential. However, prohibitively large number of process parameters and complex thermo-physical phenomenon significantly influence the microstructural features, which in turn affect the torsional performance of printed Ti-6Al-4V components. In this study, the crystallographic structural features behavior of SLM-processed Ti-6Al-4V alloy components was investigated for high-performance loading applications. X-ray diffraction (XRD) analysis of the 3D-printed SLM Ti-6Al-4V alloy specimens revealed crystallite sizes ranging from 687 to 2376 nm along the printed surface in the horizontal position (XY plane) and from 500 to 3747 nm along the part-building direction (Z-axis). Due to the associated microstrain effect, the printed surfaces in the horizontal position exhibited a region of tensile strain (2.440 × 10⁻⁴), whereas those parallel to the part-building direction exhibited region of compressive strain (−0.3057 × 10⁻⁴) during layer deposition. The printed surfaces demonstrated a higher degree of crystallinity in the vertical-position (96.9%) while the horizontal position exhibited a more amorphous structure (67.5%), suggesting that greater crystalline region develops along the part-building direction of the SLM process. Furthermore, the tensile and torsional yield strengths in the horizontal orientation (550 MPa and 308 MPa, respectively) were slightly higher than those in the vertical directions (540 MPa and 306 MPa, respectively), indicating a marginally better mechanical resistance in the horizontally oriented features compared to the vertically oriented ones.