Unveiling the impact of layerwise laser preheating on microstructure and mechanical response in laser powder bed fusion

• Published in: Journal of materials science Vol. 58; no. 45; pp. 17362 - 17382
• Main Authors: Tanrikulu, Ahmet Alptug, Ganesh-Ram, Aditya, Farhang, Behzad, Amerinatanzi, Amirhesam
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.12.2023; Springer Nature B.V
• Subjects: Anisotropy; Beds (process engineering); Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Cooling rate; Crystallography and Scattering Methods; Directional solidification; Heating; Homogeneity; Isotropy; Lasers; Material properties; Materials Science; Mechanical analysis; Melting; Metals & Corrosion; Microstructure; Modulus of elasticity; Polymer Sciences; Powder beds; Solid Mechanics; Thickness; Ultimate tensile strength
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-023-09066-2

A major limitation of the laser powder bed fusion (LPBF) process for Ti–6Al–4V is the anisotropic mechanical response caused by directional solidification during fabrication. This anisotropy can hinder the functionality and performance of components produced using LPBF. In this study, we investigated tailoring component microstructures through layerwise laser-assisted preheating during the LPBF process. The aim of this study is to modify the microstructure of Ti–6Al–4 V during LPBF by implementing an additional laser scan prior to the melting scan to enhance the isotropy and mechanical strength of the material by controlling the solidification and cooling rates. We designed and tested various energy densities for preheating scans and subsequently characterized the fabricated parts to examine the effects of layerwise preheating on microstructure and material properties. Our results demonstrate that layerwise preheating significantly reduces porosity and alters the β grain morphology from polygonal to square or circular shapes. Additionally, a shift in the predominant texture for α / α ′ phases, lath thickness, and lattice distortion was observed. Preheating also resulted in reduced anisotropy, as evidenced by the decreased difference between α / α ′ phases lath thicknesses in different planes. Notably, preheating led to enhancements in both the modulus of elasticity and ultimate tensile strength (UTS). These findings hold substantial implications for the design of materials with improved strength, microstructure, and homogeneity in LPBF processes.