Changes in the microstructure and mechanical properties of additively manufactured AlSi10Mg alloy after exposure to elevated temperatures

• Published in: Materials characterization Vol. 137; pp. 119 - 126
• Main Authors: Michaela, Fousova, Drahomír, Dvorsky, Institute of Physics, Academy of Sciences of the Czech Republic, Alena, Michalcova, Dalibor, Vojtech
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.03.2018
• Subjects: Additive manufacture; AlSi10Mg; ALUMINIUM COMPOUNDS; Elevated temperatures; ELONGATION; ENERGY-LOSS SPECTROSCOPY; HARDNESS; HEAT TREATMENTS; MAGNESIUM COMPOUNDS; MATERIALS SCIENCE; MELTING; MICROSTRUCTURE; PRECIPITATION; RECOMMENDATIONS; SCANNING LIGHT MICROSCOPY; Selective laser melting; SILICON COMPOUNDS; STABILITY; STRESSES; TERNARY ALLOY SYSTEMS; TRANSMISSION ELECTRON MICROSCOPY; YIELD STRENGTH; Elevated temperatures; Additive manufacture; AlSi10Mg; Selective laser melting
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2018.01.028

The additive manufacture (AM) of the AlSi10Mg alloy has become the subject of considerable attention, especially for production of complex parts in engines. Because such parts can be exposed to elevated temperatures during operation, material stability is very important, but as yet little is known about it in relation to AM. Here, we studied changes of the AlSi10Mg alloy produced by selective laser melting (SLM) after its exposure to temperatures between 120 and 180 °C. At each temperature, hardness evolution was measured, with hardness increasing over time. The maximum hardness state obtained at 160 °C was selected for further studies comprising microstructural analysis by scanning and transmission electron microscopy, chemical composition analysis and mechanical properties assessment. Transmission microscopy revealed nano-scale acicular precipitates that caused a slight increase in the yield strength of the alloy together with a significant drop in elongation. Electron energy loss spectroscopy (EELS) and energy dispersive spectroscopy (EDS) showed that the precipitates surprisingly consisted of pure Si. To provide a comparison, conventional regimes of heat treatment (stress-relief and T6) were applied. Despite a considerable loss in mechanical performance, thermal instability was no longer observed. Overall, our results indicate that operating temperatures are a key factor in ensuring the smooth operation of AM parts of the AlSi10Mg alloy. In respect to that, we offer recommendations for their industrial use. •Elevated temperatures above 120 °C brought changes to the AM AlSi10Mg alloy.•A maximum hardness state obtained at 160 °C/5 h was thoroughly tested.•Hardness increased by 15% and TYS by 5%, but elongation dropped by 60%.•Pure Si precipitates were responsible for the observed changes.