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Time-Resolved Absorptance and Melt Pool Dynamics during Intense Laser Irradiation of a Metal
Brian J Simonds1, Jeffrey Sowards1, Josh Hadler1
1National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA.
Physical Review Applied
|March 3, 2020
Summary
Understanding laser-induced changes in metal absorptance is crucial for industrial processes. This study measures dynamic absorptance during laser spot welding, revealing key phenomena like melt and keyhole formation.
Area of Science:
- Materials Science
- Laser Physics
- Manufacturing Engineering
Background:
- High-irradiance lasers alter metal reflectivity, impacting industrial applications like welding and additive manufacturing.
- Accurate measurement of time-dependent absorptance is critical for understanding light-matter interactions and optimizing manufacturing processes.
- Existing methods for measuring dynamic optical absorptance are limited, creating a need for improved experimental techniques.
Purpose of the Study:
- To measure the time-dependent optical absorptance of 316L stainless steel during laser spot welding.
- To investigate the physical phenomena occurring during laser-induced metal transformation.
- To provide accurate input data for laser material processing simulations.
Main Methods:
- Utilized an integrating-sphere apparatus to measure time-dependent reflected light during a 10-ms laser spot weld.
- Calculated dynamic absorptance for 1070-nm laser irradiation on 316L stainless steel.
- Analyzed weld-nugget cross sections to correlate optical measurements with physical changes.
Main Results:
- Achieved high time resolution (sub-microsecond) measurements of laser absorptance.
- Identified specific conditions for melt pool and keyhole formation based on absorptance dynamics.
- Demonstrated that calorimetry underestimates absorbed energy due to material loss during welding.
Conclusions:
- The developed method enables precise measurement of dynamic absorptance during laser welding.
- The findings provide crucial data for validating and improving laser material processing models.
- This research enhances fundamental understanding and practical application of laser-metal interactions.
