What Post-Processing Steps Are Typically Used for SLM-Printed Ti-6.5Al-1Mo-1V-2Zr Parts?

Stress Relief and Hot Isostatic Pressing

The initial critical step for SLM-printed TA15 titanium alloy is stress relief annealing immediately after the build process to prevent distortion. This is followed by Hot Isostatic Pressing (HIP), which is particularly crucial for aerospace-grade components. The HIP cycle operates at precise temperatures and pressures to eliminate internal porosity, lack-of-fusion defects, and micro-voids inherent to the SLM process. For TA15 alloy, this treatment not only achieves near-theoretical density but also initiates the transformation of the martensitic α' phase formed during rapid solidification toward a more stable and ductile α+β microstructure.

Solution Treatment and Aging

Following HIP, a specialized heat treatment regimen is applied to optimize the mechanical properties. TA15 responds to solution treatment in the α+β phase field (typically 900-980°C) followed by controlled aging. This process dissolves unstable phases and promotes the formation of a fine, equiaxed α+β microstructure with optimal phase distribution. The precise thermal profile is critical for achieving the desired balance between high-temperature strength, creep resistance, and fracture toughness required for aerospace applications where this alloy is predominantly used.

Precision Machining and Surface Enhancement

After thermal processing, components require precision CNC machining to achieve final dimensional tolerances on critical features. The as-built surface with adhered powder particles is removed to eliminate potential fatigue initiation sites. For components with complex internal structures, abrasive flow machining may be employed to smooth internal passages. Shot peening is frequently applied as a final surface enhancement to induce beneficial compressive stresses that significantly improve fatigue performance, particularly important for rotating components and airframe structures.

Quality Validation and Certification

Comprehensive material testing and analysis validates the post-processing effectiveness. This includes metallographic examination to verify complete α+β transformation and absence of defects, mechanical testing to confirm tensile and fatigue properties meet aerospace specifications, and non-destructive inspection (ultrasonic or X-ray) to certify internal integrity. For mission-critical components in military and defense applications, additional certification testing is typically required.