Work

Effects of heat treatment below beta transus temperature on the microstructure and mechanical properties of Ti–6Al–4V alloy fabricated by selective laser melting

Year: 2025

Type: article

Abstract: Ti-6Al-4V alloy fabricated via selective laser melting (SLM) inherently develops high residual stresses due to rapid cooling and steep thermal gradients. To address this, stress-relief (SR) heat treatment was performed below the β-transus temperature (0.3–0.5 Tm) to enable atomic diffusion without triggering full phase transformation. This study investigates the effects of SR treatment on microstructure evolution, dislocation density, residual stress, and mechanical properties. Residual stress was quantitatively evaluated via X-ray diffraction, while dislocation density was indirectly assessed using Kernel Average Misorientation from EBSD analysis. With increasing SR temperature, lattice distortion was gradually relieved, and a notable decrease in dislocation density began at 550 °C. A significant reduction in residual stress approximately 50% compared to the As-Built condition was observed even at 350 °C and nearly eliminated at 650 °C. Microstructural recovery of α′ martensite into equilibrium α and β phases began at 550 °C, resulting in a dual-phase α + β structure above 650 °C. Correspondingly, tensile strength declined and ductility increased. Overall, sub-transus SR treatment effectively relieved internal stresses, refined the microstructure, and improved mechanical balance, making it a practical approach for enhancing the performance of SLM Ti-6Al-4V components.

Source: Journal of Materials Research and Technology

DOI: 10.1016/j.jmrt.2025.10.013