Titanium alloys, and particularly Ti-6Al-4V, are indispensable in aerospace and medical industries. Their merit lies in their unique combination of high strength, low weight, corrosion resistance, and biocompatibility.
But despite their widespread use, engineers have long faced a persistent problem: the trade-off between strength and ductility. This compromise is especially pronounced in parts fabricated via Laser Beam Powder Bed Fusion (LB-PBF), one of the most widely adopted metal additive manufacturing processes. While LB-PBF often produces titanium parts with impressive strength exceeding 1GPa, their ductility is typically limited – a critical barrier to wider adoption in high-performance sectors.
Evaluating the microstructure of Ti-6Al-4V is far from straightforward. During LB-PBF, the alloy undergoes rapid heating and cooling, which triggers a series of phase transformations. As the high-temperature β-phase solidifies and then transforms into α or α′ martensite, it creates a microstructure that is both complex and hierarchical. At the top level sit the prior β-grains, inherited from the initial solidification stage. Within each β-grain, colonies of α or α′ variants form, which further subdivide into fine lamellae or martensitic laths on the sub-micron scale. This hierarchy (shown in fig.1) means that performance is shaped at multiple levels at once. It also means that the original solidification conditions are often concealed, making evaluation difficult and obscuring the role of prior β-grains. For decades, this complexity made it hard to establish the process-microstructure- property relation, specifically pinpointing which level of the hierarchy mattered most.
