This paper presents a study of the selective laser melting (SLM) process of quasicrystalline Al-Cu-Fe-Cr powder. The influence of laser exposure parameters on the morphology and structure of the formed layers is studied. Particular attention is paid to the transition from single-layer to multilayer formation, which is an important step towards the production of bulk quasicrystalline parts using the SLM method.
Quasicrystals, which have unique physical and chemical properties, are of considerable interest for various applications, including protective coatings, catalysis, and thermoelectric devices. Selective laser melting is a promising method for manufacturing complex geometrically-shaped products from powder materials, including quasicrystals.
The starting material was Al-Cu-Fe-Cr powder of quasi-crystalline composition. SLM experiments were carried out on a setup equipped with a fiber laser. Parameters such as laser power, scanning speed and track spacing were varied. The morphology and structure of the formed layers were studied using optical and scanning electron microscopy, as well as X-ray diffraction.
This work is devoted to studying the influence of process parameters of selective laser melting (SLM) on the formation of the microstructure of quasicrystalline (QC) coatings of the Al-Cu-Fe-Cr system. X-ray diffraction analysis of the samples demonstrates that the phase composition of the SLM coating is represented mainly by Al-Cu-Fe-Cr quasicrystals and a solid solution of α-Al (CuFeCr). It was found that an increase in the laser energy or coating thickness leads to a decrease in the volume fraction of the QC phase α-Al91Fe4Cr5 and an increase in the content of QC d-Al65Cu20Fe10Cr5 and the crystalline phase θ-Al2Cu.
The paper also analyzes the process of crack formation during layer-by-layer coating application. It is shown that for coatings with a fixed number of layers, an increase in laser power helps to reduce the number of pores and spherical particles due to improved material melting. At the initial stage of coating growth, with an increase in the number of layers (or thickness), a significant decrease in the number of pores and spherical particles is observed, which is due to the slow process of melt solidification. However, with an increase in the number of layers from 10 to 20, the porosity stabilizes, and large pores, microcracks and fractures appear, especially pronounced in the sample obtained at a lower laser power. In the transition zone between the substrate and the coating, a wavy structure is formed, consisting mainly of Al and QC phases, which is explained by the Marangoni effect.
Studies of single-layer formation have shown that the optimal parameters of laser action allow obtaining dense and homogeneous layers. When switching to multilayer formation, a change in the surface morphology and microstructure is observed. An important aspect is the control of the substrate temperature and interlayer adhesion to prevent deformations and cracks.
The presented results demonstrate the possibility of forming quasicrystalline layers by the SLM method. Further studies will be aimed at optimizing the process parameters to obtain volumetric products with specified properties.
Author: Yingqing Fu, Nan Kang, Hanlin Liao, Yang Gao, Christian Coddet
Institute: Department of Material Science and Engineering, Dalian Maritime University, 116026, Dalian, China, University of Burgundy – Franche-Comté, IRTES EA7274, F-90100 Belfort, France