Selective laser melting (SLM) is a revolutionary additive manufacturing method offering unprecedented freedom in creating complex geometries from metal powders. In the context of materials science, SLM provides a unique opportunity for the in-situ synthesis of composite materials that combine various functional properties in a single product. In particular, the creation of aluminum (Al) matrix composites reinforced with nanocrystals (NC) is of considerable interest, since it combines the lightness of aluminum with the increased strength and wear resistance provided by NC. The Al-Fe-Cr system is promising for the creation of such composites due to the formation of Fe-Cr intermetallics with high hardness and temperature stability.
This study focuses on the development and optimization of the SLM process for the in-situ synthesis of Fe-Cr nanocrystal-reinforced aluminum composite. A powder mixture of Al, Fe, and Cr was used as the starting material and its composition was carefully optimized to achieve the desired microstructure of the composite. The SLM parameters, such as laser power, scanning speed, and track spacing, were selected to ensure complete melting of the powder and the formation of Fe-Cr intermetallic phases in the aluminum matrix.
This material was created using selective laser sintering (SLM) using a powder mixture. Based on our previous research, we performed parametric optimization with an emphasis on laser scanning speed. Using optimized parameters, we obtained a sample that was almost completely dense (99.7%), free of cracks and possessing an ultra-fine microstructure.
During the work it was established that with a decrease in the laser scanning speed a phase transition occurs from decagonal quasicrystalline (QC) Al-Fe-Cr composites with a Cu25Fe10Cr5 metal matrix to icosahedral QC Al91Fe4.
Differential scanning calorimetry analysis demonstrated that the QC phase remains stable up to 500°C. The effect of annealing temperature on the microstructure and mechanical properties of the material was then studied.
The obtained results showed that QC particles prevent recrystallization and grain growth of α-Al during annealing. In addition, the growth of QC particles, leading to the formation of a porous structure, causes an increase in Young’s modulus and a decrease in plasticity.
The results show that SLM allows for the successful synthesis of Al/NC-Fe-Cr composite with uniform distribution of nanocrystals in the aluminum matrix. Microstructural analysis performed using scanning and transmission electron microscopy revealed the formation of Fe-Cr intermetallic phases with sizes ranging from 50 to 200 nm. Mechanical tests demonstrated a significant increase in the hardness and strength of the composite compared to pure aluminum. The results obtained open up broad prospects for the creation of new high-performance materials for aerospace, automotive and other industries.
Author: N. Kanga, M. ElMansori, X. Lin, F. Guittonneau, H. L. Liao, W. D. Huang, C. Coddet
Institute: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an, Shaanxi, 710072, PR China, Key Laboratory of Metal High Performance Additive Manufacturing and Innovative Design, MIIT China, Northwestern Polytechnical University, Xi’an, Shaanxi, 710072, PR China, MSMP Laboratory, EA-7350, Arts et Metiers ParisTech, Aix en Provence, 13617, France, University Bourgogne Franche-Comte, IRTES EA7274, F-90100, Belfort, 90400, France, Texas A&M Engineering Experiment Station, College Station, TX, 77843, USA