Solidification Behavior of Fe-6.5Si Alloy Powder for AM-SLM Processing, as Assessed by Differential Scanning...

Area of Science:

• Materials Science
• Metallurgy
• Additive Manufacturing

Background:

• High-silicon electrical steel is crucial for magnetic applications.
• Additive Manufacturing (AM) requires optimized processing of small powder volumes.
• Near-net-shape processing of Fe-Si alloys is increasingly important.

Purpose of the Study:

• To investigate the thermal behavior of a high-alloy Fe-Si powder for AM applications.
• To understand the melting and solidification characteristics of Fe-6.5wt%Si powder.
• To identify microstructural changes and their impact on magnetic properties.

Main Methods:

• Characterization of Fe-6.5wt%Si spherical powder using chemical, metallographic, and thermal analyses.
• Surface oxidation assessment via metallography and Field Emission Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy (FE-SEM/EDS).
• Melting and solidification behavior evaluation using Differential Scanning Calorimetry (DSC) and Scheil-Gulliver solidification modeling.

Main Results:

• Surface oxidation was observed on as-received powder particles.
• Significant silicon loss occurred during powder remelting.
• Solidification resulted in needle-shaped eutectics within a ferrite matrix, with silica presence confirmed by modeling.
• Thermodynamic calculations predicted exclusive ferrite precipitation for binary Fe-6.5wt%Si, contrasting with the ternary alloy's silica formation.

Conclusions:

• Thermal processing of Fe-6.5wt%Si powder for AM leads to silicon loss and undesirable silica phase formation.
• The presence of silica negatively affects the magnetic properties of soft magnetic Fe-Si materials.
• Further research is needed to mitigate silicon loss and silica formation for effective AM of electrical steels.