Multimaterials can be defined as components or parts produced using more than one material within the same manufacturing process. Among the multimaterials systems explored, combinations of materials with contrasting properties, such as Al or Cu alloys with high thermal conductivity together with materials offering higher mechanical strength, including steels or Ni-based alloys, have gained significant attention due to their applications in advanced industries such as aerospace, nuclear engineering, electrical mobility, among others [1].

Laser Powder Bed Fusion (LPBF) is an additive manufacturing (AM) techniques which allow the production of multimaterials with complex geometries by the fabrication of composites that combine dissimilar metallic alloys within a single build process. This capability expands design freedom and makes it possible to tailor local properties within a component. However, the differences in thermal expansion between the constituent materials together with the rapid, localized heating and cooling cycles inherent to LPBF can lead to the development of significant residual strains in the final parts.

Bragg-edge neutron imaging (BEI) offers a powerful and non-destructive approach for analysing residual strain in multimaterials composites produced by AM. Unlike based diffraction methods, BEI provides full-field maps of lattice spacing variations with high spatial resolution, on the order of 100 µm, allowing strain gradients to be resolved across interfaces and complex geometries. This can be observed in Fig. 1 where the residual strain maps were determined on a steel lattice of AISI 316L/CuCrZr composite [2].

Figure 1. Example of the as-printed 316L lattices after casting with CuCrZr (left), alongside the corresponding strain maps in microstrain [μɛ] for an empty 316L lattice (centre) and the strain evolution following CuCrZr casting (right).

In this study, the residual strains maps in different combinations of multimaterials composites, produced by LPBF and by a hybrid manufacturing approach, were studied. The strain maps and microstructure of the composite parts were analysed using the Frame Overlap Bragg Edge Imaging (FOBI) technique [3] at POLDI (Pulse OverLap DIffractometer), the time-of-flight diffractometer at SINQ spallation neutron source, Switzerland.

References
[1] A. Nazir et al., Materials & Design, 2023, 226, 111661
[2] A. Baganis et al., Journal of Materials Research and Technology, 2024, 33, 7260–7273.
[3] M. Busi et al., Scientific Reports, 2020, 10, 14867.

Florencia Malamud (Ph.D.)