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

## TL;DR

This study examines how preheating the base plate affects the laser printing of an aluminum alloy, finding that higher temperatures can change crack patterns and material properties.

## Contribution

The paper reveals that base plate preheating does not reduce hot cracking in EN AW 7075 and may alter crack mechanisms at high temperatures.

## Key findings

- Moderate preheating (100–200 °C) does not significantly reduce crack density or change grain morphology.
- Preheating at 400 °C leads to columnar crack networks, modified grain orientation, and reduced hardness.
- Zn and Mg evaporation occurs consistently during processing, regardless of preheating temperature.

## Abstract

The influence of base plate temperature (25, 100, 200, and 400 °C) on the laser powder bed fusion processing of EN AW 7075 was systematically investigated using microstructural characterisation (LM, SEM, EBSD, GROD), chemical analysis, hardness testing, and thermal simulations across a broad range of process parameters. Moderate preheating at 100 °C and 200 °C showed no significant reduction in crack density or changes in grain morphology compared to processing without preheating. At the highest studied temperature—400 °C—a transition to columnar crack networks was observed, accompanied by modified grain orientation, pronounced stress relaxation, and reduced hardness. Independent of preheating temperature, consistent evaporation of Zn (~1 wt.%) and Mg (~0.3 wt.%) occurred during processing. Thermal simulations qualitatively supported the experimental observations, indicating increased thermal retention and displacement with increasing preheating temperature. The results demonstrate that base plate preheating alone is insufficient to suppress hot cracking in EN AW 7075 and may promote alternative crack-growth mechanisms at elevated temperatures, highlighting the need for alternative alloy or process design strategies.