Phase Transformation Behaviour and Mechanical Properties of Ti-6Al-4V Alloy Fabricated by Selective Laser Melting: Relevance to Nigerian Biomedical and Aerospace Applications

This study investigates the phase transformation behaviour and resulting mechanical properties of Ti-6Al-4V alloy specimens fabricated by selective laser melting (SLM), with reference to the emerging biomedical implant and aerospace fastener application needs of Nigerian hospitals and aviation maintenance operations. Ti-6Al-4V is the most widely used titanium alloy globally, and additive manufacturing via SLM is transforming its processing landscape, yet characterisation data relevant to Nigerian application contexts and available laser powder bed facilities is limited in the national literature. Specimens are fabricated on a research-grade SLM platform at a university laboratory with varied layer thickness (30 and 60 micrometres), laser power (150 and 200 W), and scan strategy (unidirectional and bidirectional). Microstructural characterisation is performed by optical microscopy, SEM-EBSD, and XRD to quantify alpha and beta phase fractions, grain morphology, and texture. Post-build stress relief anneal (600 degrees Celsius) and full annealing (800 degrees Celsius) treatments are evaluated for microstructural modification. Tensile and fatigue properties are measured on as-built and heat-treated specimens. Results show that SLM Ti-6Al-4V achieves tensile properties meeting ASTM F2924 implant material requirements following 800 degrees Celsius annealing, with yield strength of 925 MPa and elongation of 12 percent. Keywords: Ti-6Al-4V, selective laser melting, phase transformation, biomedical, Nigeria.