Multi-build orientation effects on microstructural evolution and mechanical behavior of truly as-built selective laser melting Ti6Al4V alloys

Abstract

The unique combination of lightweight, strength, corrosion resistance, high-temperature resistance, and biocompatibility make Ti6Al4V alloy an important material in metal contact of solar cells, and selective laser melting (SLM) enables the production of Ti6Al4V parts complex geometries that would be difficult or impossible to produce using traditional manufacturing methods. The build orientation of SLM process presents an essential effect on the quality of the produced parts, and thus, in this study it investigates the impact of multi-build orientation (0°, 30°, 45°, 60°, 90°) on the microstructural evolution and mechanical behavior of truly as-built Ti6Al4V alloys produced by SLM. The microstructure analysis revealed the presence of ordered subsurface pores, located at a distance of about 50 μm–150 μm from the sample surface. The microstructure consisted primarily of α′ martensite with a small amount of β phase. Massive transformation was observed in the 30° and 45° samples, with corresponding grain sizes of 5 μm and 10 μm, respectively. To be specific, the content of β phase and ultimate tensile strength (UTS) varied with the sample orientation, and the 45° build orientation exhibited the highest content of β phase with value of approximately 2.8%, but also the lowest UTS and elongation, which were 1161 MPa and 3.99%, respectively.

Keywords

• Selective laser melting
• Ti6Al4V
• Multi-build orientation
• Microstructural evolution
• Mechanical behavior