Creating Heterostructures via Laser Powder Bed Fusion Using Titanium and Stainless Steel Mixtures
Date
Authors
Supervisor
Item type
Degree name
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
This study addresses the challenge of breaking the trade-off dilemma between strength and ductility in additively manufactured Titanium (Ti) products. By leveraging concentration non-uniformity and controlled diffusion during in-situ alloying of unalloyed titanium (CP-Ti) and 316L stainless steel (SS316) powders via laser powder bed fusion (LPBF), we formulated a novel Fe-containing alloy with improved printability and enhanced mechanical performance. The microstructure of the as-built Ti alloy comprises a heterostructure of nano-scaled martensitic α′ within the micro-scaled equiaxed prior-β grains, resulting from rapid solidification inherent in LPBF. Since the modified laser-powder bed fusion in this work lacks a pre-heating function, a stress-relief annealing process was conducted to enhance the mechanical properties of the as-built parts. The annealed in-situ alloyed Ti-Fe achieves a superb balance between strength and ductility, with an ultimate tensile strength (UTS) of approximately 1118.0 MPa and an elongation of ∼9.0 %. This study provides insights for designing high-performance Ti alloys with heterostructures using a mixture of elemental powder and alloyed powders via LPBF. The significance of concentration non-uniformity and diffusion during solidification is highlighted, demonstrating how these factors contribute to the formation of superior heterostructures through additive manufacturing.