Phase Transformation Behaviors and Dislocation Evolutions of an Additively Manufactured Ti-6Al-4V Alloy under Annealing Treatment

Abstract

Post annealing treatment is generally needed for additively manufactured titanium alloy to decompose metastable phases, alleviate residual stress, and improve ductility. In this work, in-situ electrical resistivity and line profile analysis of X-ray diffraction were utilized for monitoring phase transformation behaviors and dislocation evolutions of a laser powder bed fusion-built Ti-6Al-4V alloy under post annealing treatment. Besides, hardness and tensile tests were adopted for revealing the effects of phase transformation and dislocation evolutions on the mechanical properties. The results indicated that post annealing treatment decomposed martensitic α′ into lamellar α + β and eliminated dislocations efficiently. The martensite decomposition rate increased with the annealing temperature. Annealing at 700 °C for 4 h eliminated 98% of the dislocations, and further annealing has only a limited influence on the dislocation density. Annealing at 700 °C for 16 h is beneficial for achieving a high ductility of 10.3% owing to the favorable equilibrium lamellar α + β microstructure. These findings provide valuable insights for optimizing post annealing treatment procedures to enhance the mechanical properties of additively manufactured Ti-6Al-4V alloys.

Enhancing Mechanical Properties: Exploring the Effect of Annealing Temperature on Wire Arc Additively Manufactured High-Strength Steel

“…However, the unique thermal cycling process of additive manufacturing leads to non-uniformity in the micro-grain scale, which can have an impact on the mechanical properties, such as non-uniform strain [31]. Therefore, an overall annealing treatment is required to homogenize the grain size, eliminate residual stresses, and further improve the strength and toughness of the additively manufactured components [32][33][34]. However, few studies have investigated the effect of heat treatment on the microstructure and mechanical properties uniformity of additively manufactured laminated alloys, which are expected to have higher uniformity than additively manufactured single alloys.…”