Influence of Base Plate Preheating on Laser Powder Bed Fusion-Processed EN AW-7075 Aluminium Alloy

Area of Science:

• Materials Science
• Additive Manufacturing
• Metallurgy

Background:

• Laser Powder Bed Fusion (LPBF) is a key additive manufacturing technique.
• EN AW 7075 is a high-strength aluminum alloy prone to hot cracking during LPBF.
• Controlling thermal conditions, like base plate temperature, is crucial for mitigating defects.

Purpose of the Study:

• To investigate the effect of base plate temperature on LPBF of EN AW 7075.
• To determine if preheating can suppress hot cracking and improve microstructure.
• To understand the underlying mechanisms of crack formation at different temperatures.

Main Methods:

• Systematic investigation of EN AW 7075 LPBF across various base plate temperatures (25-400 °C).
• Utilized microstructural characterization (LM, SEM, EBSD, GROD), chemical analysis, and hardness testing.
• Employed thermal simulations to correlate with experimental observations.

Main Results:

• Moderate preheating (100-200 °C) did not significantly reduce crack density or alter grain morphology.
• High preheating (400 °C) induced columnar crack networks, modified grain orientation, and reduced hardness.
• Consistent evaporation of Zinc and Magnesium occurred regardless of preheating temperature.
• Thermal simulations confirmed increased thermal retention and displacement with higher preheating.

Conclusions:

• Base plate preheating alone is insufficient to prevent hot cracking in EN AW 7075.
• Elevated temperatures can introduce alternative crack growth mechanisms.
• Alternative alloy compositions or advanced process design strategies are required for successful LPBF of this alloy.