Multi-scale microstructure high-strength titanium alloy lattice structure manufactured via selective laser melting

Area of Science:

• Materials Science
• Additive Manufacturing
• Mechanical Engineering

Background:

• Ti6Al4V alloy is a critical material in aerospace and biomedical applications.
• Lattice structures offer high strength-to-weight ratios but require optimized fabrication and post-processing.
• Selective laser melting (SLM) enables complex geometries but can introduce microstructural defects and residual stresses.

Purpose of the Study:

• To investigate the tensile performance of Ti6Al4V alloy lattice structures fabricated by SLM.
• To evaluate the effect of a specific heat treatment (double solution-aging) on microstructure and mechanical properties.
• To correlate microstructural evolution with tensile strength enhancement.

Main Methods:

• Design of a face-centered cubic unit cell with vertical struts (F2CCZ) lattice structure.
• Fabrication of lattice structures using selective laser melting (SLM) with varying aspect ratios.
• Application of a double solution-aging heat treatment to SLM-fabricated samples.
• Microstructural analysis and tensile testing to characterize mechanical performance.

Main Results:

• SLM-fabricated Ti6Al4V alloy primarily contained acicular α' martensite with high dislocation density.
• Heat-treated (HT-ed) alloys exhibited α and β phases with multi-scale α laths and nano-scale β particles.
• Tensile strength increased significantly from 140 ± 18 MPa (as-SLM) to 229 ± 5.1 MPa (HT-ed, aspect ratio 4).
• The orientation relationship [113]_β//[1210]_α was observed in the heat-treated microstructure.

Conclusions:

• The specialized heat treatment effectively homogenizes the microstructure of SLM-fabricated Ti6Al4V alloy.
• The heat treatment significantly improves the tensile strength of Ti6Al4V alloy lattice structures.
• This study demonstrates a viable pathway for enhancing the mechanical performance of additively manufactured titanium alloys.