DOCTORAL CANDIDATE
Irvichetty Guru Santhosh

SUPERVISORS
Nicolas Saintier, École Nationale Supérieure d’Arts et Métiers (ENSAM)
Gwenaelle Proust,The University of Sydney (USYD)

Mechanics, Materials

Selective Laser Melting (SLM) is a metal additive manufacturing (AM) process that can revolutionize material fabrication by enabling the creation of architectured materials with intricate internal structures and tailored properties. SLM technology involves the layer-by-layer fusion of metal powder using a high-power laser, enabling the design of intricate structures. This precise control over the material deposition allows for the fabrication of complex geometries and internal architectures that are challenging or impossible to achieve using traditional manufacturing methods. This process, however, can lead to inherent defects such as residual stresses, porosities, and microstructural irregularities, which negatively impact the mechanical properties of the final product.
Furthermore, architectured structures obtained by SLM can be specifically designed to be used as structural components under complex fatigue loadings. These structures’ light weight and capability to dissipate energy are advantageous for developing a new class of components. These materials are not homogeneous throughout but comprise various patterns, lattices, or gradient structures. To conceive more efficient and robust structures, it is necessary to understand further the effect of the specific microstructures induced by the SLM process due to rapid solidification rates and high thermal gradients. Indeed, the microstructures created in the thin structural elements (walls and struts) can induce local anisotropy that may govern the overall behaviour of the lattice under cyclic loadings.

This project aims to optimize the microstructures obtained by SLM with respect to the mechanical behaviour (static, cyclic) of thin-walled structures by optimizing the post-treatment processes. There needs to be a more detailed understanding of the role of microstructural length scales on the mechanical behaviour of architectured materials under cyclic loadings and their dependence on post-processing parameters.
A methodology will be developed: (1) to understand the microstructures of SLM-processed metallic alloys using different material characterization techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD), (2) to characterize the quasi-static and fatigue behaviour of architectured materials produced by the SLM process, (3) to develop specific post-treatments such as hot isostatic pressing (HIP), heat treatments or case hardening treatments and characterize the obtained microstructures and the cell morphologies using micro-computed tomography, (4) to evaluate the effect of post-treatments on the mechanical behaviour of lattice structures and (5) to establish the link between the post-treatment process, the microstructures and the mechanical behaviour of architectured materials.

This research endeavours to unlock the full potential of additive manufacturing, creating materials with exceptional mechanical properties and multifaceted applications. Successful implementation of these post-treatment routes could open new avenues for producing high-performance, lightweight structures with tailored mechanical properties. Aerospace, automotive, and medical industries could benefit significantly from the resulting materials, offering improved efficiency, reduced weight, and enhanced functionality.