Study of the mechanical behavior and solidification of modified 316L steels manufactured through additive manufacturing

• Grant number: 24/19365-3
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: April 01, 2025
• End date: July 31, 2025
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Piter Gargarella
• Grantee: Luiz Henrique Quinquiolo Ribeiro de Lima
• Supervisor: Michael Joseph Kaufman
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Institution abroad: Colorado School of Mines, United States
• Associated to the scholarship: 23/14592-9 - Study of the Mechanical Behavior and Solidification of Modified 316L Steels Manufactured through Additive Manufacturing, BP.MS

Abstract

Additive Manufacturing (AM) processes, such as Laser Powder Bed Fusion (L-PBF), also known as Selective Laser Melting (SLM), enable the production of highly dense parts with complex geometries, reduced material waste, and minimal need for post-processing. Due to its characteristics, such as high thermal conductivity, favorable solidification behavior, and excellent mechanical and corrosion resistance, the austenitic stainless steel AISI 316L is one of the most studied and widely used materials in AM. Results from the DEMa/UFSCar research group show that the addition of boron in steels alters the solidification of steels produced by LPBF, inducing a transition from a columnar grain structure, typical of AM processes, to an equiaxed structure, with the formation of an interconnected network of borides. This transition is significant because equiaxed grains offer more isotropic mechanical properties, reduce the likelihood of defects such as cracks, and improve the material's overall performance under stress. Additionally, the occurrence of deformation-induced phase transformation from austenite to martensite was also observed in the boron-modified material. This phenomenon is known as Transformation-Induced Plasticity (TRIP) effect, which leads to increased strength and ductility, delaying necking. This effect is characterized by high work-hardening rates, high post-yield plasticity, and energy absorption capacity, making it desirable for aerospace, automotive, and other demanding applications. Considering this, at the Colorado School of Mines in Golden, Colorado, USA, several advanced tools are available to investigate these new steels. The laboratory is equipped with a TESCAN S8252G RAMAN SEM, which can be coupled with a straining stage for in situ Scanning Electron Microscope (SEM) and Electron Backscatter Diffraction (EBSD) analysis, enabling detailed investigation of microstructural changes during deformation to study the TRIP effect. Additionally, a Panalytical X-ray diffractometer is available for in situ X-ray Diffraction (XRD) analysis, providing further insights into the phase transformations induced by deformation. In relation to the solidification process, a Focused Ion Beam (FIB) tool in the transmission electron microscope will be crucial for analyzing specific regions of the melt pool, which will help to understand the microstructural evolution and phase transformations occurring during solidification. This targeted analysis will provide valuable data to comprehend how the addition of boron alters the solidification process, transitioning from a columnar to an equiaxed grain structure. Therefore, this research internship aims to the master student spend a period at Colorado School of Mines, under supervision of Prof. Dr. Michael J. Kaufman, to gain a deeper understanding of the boron-modified 316L stainless steel, both in terms of solidification behavior and deformation-induced phase transformations, contributing to the development of high-performance materials.