Vidhiaza Leviandhika: From Process to Performance: Tailoring Materials in Laser-Based Additive Manufacturing and Processing

Abstract

Powder Bed Fusion – Laser Beam (PBF – LB) has emerged as an effective method for producing metallic components with complex geometries. Beyond its capability as a shaping technology, the process introduces unique thermal conditions that strongly influence microstructural evolution. These characteristics present both challenges and opportunities, as rapid solidification and cyclic reheating can lead to unwanted defects and non-equilibrium microstructures, while also paving new pathways for tailoring material properties.

This thesis explores how laser-based additive manufacturing can be used as a tool for controlling material behavior and component performance. The work focuses on the combined effects of compositional modification, process strategies, and post-processing treatments on microstructure, mechanical response, and tribological performance across different metallic systems.

In Ti-6Al-4V alloy, powder mixing with 316L stainless steel was used to modify phase stability, resulting in a transition from martensitic α’ to β-rich microstructures with reduced stiffness. Localized thermal control through laser rescanning enabled the formation of graded microstructures, combining a hard surface with a more compliant bulk. Surface engineering strategies were further explored through both in-situ and post-processing approaches, including nitrogen-assisted processing and hot isostatic pressing, demonstrating the formation of hard nitride-based surface layers and improved wear resistance. Fundamental aspects of microstructure formation were also investigated using single-track experiments in an Mg–Li alloy, where spatial variations in thermal conditions within the melt pool were shown to produce distinct microstructural features and corresponding variations in local mechanical response. Finally, the geometric freedom enabled by PBF-LB was explored at the component level through the fabrication of a structurally modified design, demonstrating how internal features can be used to influence effective mechanical behavior without altering the base material.

The work in the thesis shows that PBF – LB can be used beyond the fabrication of complex components. It is also a versatile platform for tailoring material properties across multiple length scales. By combining control over microstructure, surface, and geometry, this work highlights a broader approach to materials engineering in which processing is used as an active tool for achieving targeted performance.