Operando neutron diffraction reveals mechanisms for controlled strain evolution in 3D printing

Residual stresses affect the performance and reliability of most manufactured goods and are prevalent in casting, welding, and additive manufacturing (AM, 3D printing). Residual stresses are associated with plastic strain gradients accrued due to transient thermal stress. Complex thermal conditions in AM produce similarly complex residual stress patterns. However, measuring real-time effects of processing on stress evolution is not possible with conventional techniques. Here we use operando neutron diffraction to characterize transient phase transformations and lattice strain evolution during AM of a low-temperature transformation steel. Combining diffraction, infrared and simulation data reveals that elastic and plastic strain distributions are controlled by motion of the face-centered cubic and body-centered cubic phase boundary. Our results provide a new pathway to design residual stress states and property distributions within additively manufactured components. These findings will enable control of residual stress distributions for advantages such as improved fatigue life or resistance to stress-corrosion cracking. Residual stress affects most manufactured goods and is prevalent in casting, welding, and additive manufacturing. Here, the authors use operando neutron diffraction to elucidate mechanisms for lattice strain evolution during printing of a low-temperature transformation steel.

Automated summary

Residual stresses impact the performance and reliability of manufactured goods and are commonly found in casting, welding, and additive manufacturing. By utilizing operando neutron diffraction, the authors investigate the lattice strain evolution during the printing of a low-temperature transformation steel, providing insights into the mechanisms involved and enabling the design of residual stress states and property distributions in additively manufactured components.