Which Post-Processes Enhance Mechanical Properties of AlSi10Mg WAAM Parts?

T6 Heat Treatment for Microstructural Optimization

The most critical post-process for enhancing AlSi10Mg WAAM parts is T6 heat treatment, comprising solution treatment at 500-540°C followed by rapid quenching and artificial aging. This treatment transforms the coarse, columnar microstructure typical of WAAM deposition—characterized by large aluminum grains with coarse silicon networks—into a refined, homogeneous structure with spheroidized silicon particles. This microstructural transformation significantly improves tensile strength (increasing by 30-50% to 250-320 MPa), enhances ductility (from 3-5% to 8-12% elongation), and improves fatigue resistance. The solution treatment dissolves brittle intermetallic phases formed during solidification, while aging precipitates strengthening Mg₂Si particles throughout the aluminum matrix.

Hot Isostatic Pressing for Density Improvement

While less common than with superalloys, Hot Isostatic Pressing (HIP) can benefit high-integrity AlSi10Mg WAAM components. HIP at 480-520°C with 80-120 MPa pressure effectively eliminates internal porosity, lack-of-fusion defects, and micro-voids inherent to the WAAM process. This increases density to near-theoretical values (≥99.8%), enhancing fatigue strength by 40-60% and improving fracture toughness. For components subjected to cyclic loading in aerospace or automotive applications, HIP ensures reliable performance under dynamic stresses.

Stress Relief and Stabilization Treatment

WAAM-produced AlSi10Mg contains significant residual stresses from the high-heat-input deposition process. A stabilization treatment at 300-350°C relieves these stresses, preventing distortion and improving dimensional stability during subsequent machining and service. This intermediate thermal treatment also initiates silicon spheroidization and partially dissolves brittle β-phase (Mg₂Si) networks at grain boundaries. The stress relief process enhances machinability and ensures the final T6 treatment achieves uniform properties throughout the component, particularly important for large structural parts where stress concentrations could compromise performance.

Mechanical Surface Enhancement Techniques

The rough as-deposited WAAM surface contains stress concentrators that significantly reduce fatigue performance. Precision CNC machining removes 2-5mm of the surface layer, eliminating defects and creating a uniform stress-free surface. Shot peening then introduces compressive stresses that increase fatigue life by 50-100% and improves resistance to stress corrosion cracking. For components with complex internal geometries, abrasive flow machining can enhance surface finish and further improve fatigue performance by removing microscopic defects in hard-to-reach areas.

Property Validation and Quality Assurance

Comprehensive material testing and analysis validates the effectiveness of all post-processing treatments. This includes tensile testing to verify strength and ductility improvements, microstructural examination to confirm proper silicon spheroidization, and fatigue testing to validate enhanced dynamic performance. Non-destructive methods such as ultrasonic testing ensure internal soundness, while hardness mapping verifies uniform property distribution throughout the component. This systematic approach ensures AlSi10Mg WAAM parts achieve the mechanical properties required for demanding industrial applications.