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ORNL researchers have introduced OpeN-AM, a 3D printing system that monitors changing residual stress throughout manufacturing. They integrated it with infrared imaging and computer modelling offering unique insights into material behaviour during production. Additionally, they utilised low-temperature transformation (LTT) steel to track atomic movement in response to stress, be it from temperature or load, using OpeN-AM.
Residual stresses persist even after the stressor is removed and can deform or prematurely damage a material, posing significant challenges in component fabrication. This innovative experiment, developed over two years, can gauge material strain as it evolves, providing critical information about stress distribution.
“Manufacturers can customise residual stress in their components, enhancing their strength, reducing weight, and enabling more intricate designs. This technology has broad applications across various manufacturing sectors,” Plotkowski explained. “Our success validates the feasibility of this approach, showcasing the ability to apply insights from one case to anticipate solutions in others.”
The scientists employed a specialised wire-arc additive manufacturing platform to carry out operando neutron diffraction on a low-temperature transformation (LTT) metal at ORNL’s Spallation Neutron Source (SNS). Using the SNS’s VULCAN beamline, they processed the steel, collecting data at multiple points throughout the manufacturing process and post-cooling to room temperature.
They integrated diffraction data with infrared imaging for confirmation. The system was developed and constructed at the Manufacturing Demonstration Facility (MDF), a Department of Energy (DOE) Advanced Materials and Manufacturing Technologies Office user consortium. A duplicate platform at MDF was created to plan and test experiments before executing them at the beamline.
The SNS, operating a linear particle accelerator to produce neutron beams, enables atomic-scale materials analysis. The research tool they devised empowers scientists to observe the internal workings of a material as it’s being fabricated, essentially witnessing the mechanisms in real-time.
The LTT steel underwent a process where it was melted and deposited in layers. As it cooled and solidified, it underwent a phase transformation characterised by atoms rearranging and occupying different spaces, altering material properties.
Ordinarily, comprehending transformations that occur at high temperatures in a material post-processing is challenging. However, by observing the LTT steel during manufacturing, this experiment demonstrates the ability to comprehend and control the phase transformation.
The primary objective is to understand the origins of residual stresses, their causes, and how to manage them, as noted by Plotkowski.
The outcomes of this research introduce a new avenue for designing desirable residual stress states and property distributions within additive manufacturing components. It involves optimising nonuniform spatial and temporal variations of thermal gradients around critical phase transformation temperatures using process controls, as articulated by the authors.
Plotkowski envisioned a future where scientists from across the globe are drawn to ORNL to conduct similar experiments, mainly focusing on metals destined for manufacturing applications. The success of this research showcases the potential for advancements in materials science. It highlights the value of collaborative efforts and cutting-edge technologies in reshaping the landscape of additive manufacturing and materials design.
The fusion of AI, 3D printing, and advanced material analysis exemplified a testament to the remarkable capabilities that interdisciplinary collaboration can yield. This approach has the potential to redefine the way materials are designed and also underscores the crucial role that national laboratories like ORNL play in driving scientific progress.
