AlSi10Mg Aluminium Alloys In Additive Manufacturing And Laser Powder Bed Fusion

AlSi10Mg is one of the most widely used and well-understood aluminium alloys in additive manufacturing (AM), particularly in Laser Powder Bed Fusion (L-PBF) processes.

The name "AlSi10Mg" directly describes its primary alloying elements:

• Al (Aluminium): Base metal (approximately 90%).
• Si (Silicon): ~9-11%. Silicon lowers the melting point, reduces shrinkage during solidification, improves fluidity, and enhances castability and weldability. It also contributes to strength.
• Mg (Magnesium): ~0.2-0.45%. Magnesium enables precipitation hardening through the formation of Mg₂Si phases during heat treatment, significantly increasing the material's strength.

A typical composition table looks like this:

Critical Impurity: Oxygen Content
For AM powders, the oxygen content is a crucial specification not listed in standard composition tables. High-quality powder will have an oxygen content < 200 ppm (parts per million). Low oxygen is vital to prevent the formation of oxides, which can create defects, reduce mechanical properties, and cause issues during printing.

AlSi10Mg powder for AM is almost exclusively produced via Gas Atomization:

• Melting: The raw AlSi10Mg alloy is melted in a induction furnace under a controlled atmosphere.
• Atomization: The molten metal is poured through a tundish (a funnel) where a high-pressure stream of inert gas (usually Nitrogen or Argon) breaks the liquid stream into fine droplets.
• Solidification: These droplets cool and solidify into spherical particles as they fall in the atomization tower.
• Sieving and Classification: The powder is then sieved to achieve a specific Particle Size Distribution (PSD), crucial for 3D printing.

Key Powder Characteristics:

• Morphology: Perfectly spherical particles are ideal. This ensures excellent flowability, which is critical for spreading thin, uniform layers in the powder bed.
• Particle Size Distribution (PSD): The most common PSD for L-PBF is 15-45 μm or 20-63 μm. A tight distribution ensures consistent packing density and smooth recoating.
• Satellites: Small particles that are welded to larger ones. High-quality powder has minimal satellites, as they can hinder flowability.

The L-PBF process creates a unique, fine microstructure that differs from traditionally cast AlSi10Mg.

As-Built (Directly after printing):

• High Strength & Hardness: The rapid cooling (quenching) creates a super-saturated solution and a very fine cellular microstructure surrounded by a silicon network. This results in higher tensile strength and hardness compared to casting.
• Relatively Low Ductility: The as-built material can be brittle.

After Heat Treatment (T6 - Solution Heat Treated and Aged):

• Improved Ductility: Strength decreases slightly, but elongation at break increases significantly, making the part tougher and less brittle.
• Stress Relief: Removes residual stresses from the rapid heating and cooling of the printing process.

Typical Mechanical Properties (L-PBF, Vertical Orientation):

Other Properties:

• Density: ~2.67 g/cm³ (The printed part is typically >99.5% dense)
• Thermal Conductivity: ~120 - 150 W/m·K (good for heat exchangers)
• Melting Point: ~570°C - 600°C (approx.)

AlSi10Mg is the go-to material for lightweight, functional components across industries:

• Aerospace: Brackets, mounts, ducting, cabin components, satellite parts.
• Automotive: Lightweight brackets, engine components (e.g., turbocharger housings), heat exchangers, and custom parts for motorsports.
• Industrial: Robotic arms, end-effectors, jigs, fixtures, and tooling.
• Thermal Management: Heat sinks and complex, optimized heat exchangers that are impossible to make traditionally.