Tailoring Mechanical and Wear Behavior of Ti15Mo with a Gradient Isothermal ω Phase via Selective Laser Melting

This study exploits the intrinsic heat treatment (IHT) effect inherent to selective laser melting (SLM) to produce a metastable β-Ti15Mo alloy that exhibits a gradient distribution of the isothermal ω phase (ωiso) without any compositional modification. Detailed microstructural characterization reveals a systematic spatial gradient in both the volume fraction and characteristic size of nanoscale ωiso precipitates along the building direction, which directly governs the corresponding gradients in mechanical properties and wear resistance. Compression testing confirms that the compressive yield strength tracks with the ωiso evolution, ranging from 942 MPa to 1152 MPa along the building direction. Furthermore, tribological assessments conducted under phosphate-buffered saline (PBS) lubrication indicate a transition in the prevailing wear mechanism from severe adhesion to mild abrasion, accompanied by a wear rate spanning 2.06 × 10⁻⁴ to 3.06 × 10⁻⁴ mm³·N⁻¹·m⁻¹. Collectively, these findings validate a robust IHT-driven pathway for the SLM fabrication of functionally graded β-Ti implants, offering an effective strategy to reconcile the inherent trade-offs between mechanical strength, elastic modulus, and surface durability.