Abstract
Due to the rapidly degradative mechanical performance of selective laser melted (SLM) Al–12Si at elevated temperatures, an Al–12Si–Ti alloy was synthesized by SLM processing with a powder mixture consisting of Al–12Si and 1 wt% of Ti nanoparticles to improve its thermal stability at mid-temperatures (573 K). The results demonstrate that the addition of Ti nanoparticles (i) enlarges the parameter window of SLM processing (power inputs of 200–350 W and scanning speeds of 600–1600 mm/s), (ii) stimulates a columnar to equiaxed transition and refinement of grains (average grain size decreases from 9.0 μm to 1.5 μm), (iii) forms Al3Ti phase improving the thermal stability of Al–Si eutectic cell structure, and (iv) partially suppresses the precipitation of Si phase and coarsening of cell structure at elevated temperatures. These features lead to an improved yield strength of SLM Al–12Si–Ti compared with SLM Al–12Si. Specifically, SLM Al–12Si–Ti annealed at 573 K possesses a higher yield strength (297 ± 10 MPa) than SLM Al–12Si (207 ± 9 MPa) annealed at the same conditions. This study will pave the way for the design and synthesis of SLM Al alloys with improved structural and mechanical stability by minor alloying via nanoparticle addition.
| Originalsprache | Englisch |
|---|---|
| Aufsatznummer | 143833 |
| Seitenumfang | 12 |
| Fachzeitschrift | Materials Science and Engineering A |
| Jahrgang | 855.2022 |
| Ausgabenummer | 10 October |
| Frühes Online-Datum | 29 Aug. 2022 |
| DOIs | |
| Publikationsstatus | Veröffentlicht - 10 Okt. 2022 |
Bibliographische Notiz
Funding Information:P Wang would like to thank Dr. X. Zhang, and Dr. L.F. Zhang for the technical assistance and fruitful discussions concerning TEM investigations. Moreover, valuable technical support for EBSD measurements by Dr. Y. Qi, Dr. M.H. Li and Dr. X.H. Gao is gratefully acknowledged. The authors also wish to acknowledge the assistance on HRTEM observations received from the Electron Microscope Center of Shenzhen University. This work was supported by the National Natural Science Foundation of China (NSFC, No. 52105385 , and 52005340 ), the Guangdong Basic and Applied Basic Research Foundation ( 2020A1515110869 and 2022A1515010781 ) and Shenzhen international cooperation research (Grant No. GJHZ20190822095418365 ). I. Okulov acknowledges the financial support provided by the German Science Foundation under the Leibniz Program (Grant MA 3333/13-1 ). J. Eckert wants to thank the Austrian Academy of Sciences for additional support provided through the Innovation Program.
Funding Information:
To comprehensively understand the grain refining mechanism in the as-SLMed Al–12Si–Ti alloy, microstructural characterization and crystallographic investigations were conducted by TEM. Fig. 6 shows a HAADF-STEM image and the corresponding EDS maps for the SLM Al–12Si–Ti alloy. Cuboidal particles are clearly observed in the grain interior and at the grain boundaries. The size of these Ti-rich particles ranges from 30 nm to 100 nm. According to EDS analysis, these cuboidal particles contain Al and Ti (74.4 ± 0.7 at.% Al and 25.6 ± 0.7 at.% Ti). The electron diffraction patterns of ɑ-Al phase and Al3Ti phase are shown in the inset. Previous studies have shown that Al3Ti can have two different crystal structures: D022-Al3Ti (lattice constants: a = 3.85 Å and c = 8.60 Å [64]) or L12-Al3Ti (the lattice constant: a = 4.05 Å [65]). Tan et al. [66] reported that L12-Al3Ti is highly likely to form at higher cooling rate. According to the indexed diffraction patterns and EDS analysis, these cuboidal particles are confirmed as D022-Al3Ti (the lattice constants: a = 3.84 Å and c = 8.60 Å). Compared with Tan et al.'s study, the SLM Al–12Si–Ti alloy in this work was prepared at higher volume-energy density (lower cooling rate) [15]. Therefore, the lower cooling rate stimulates the formation of D022-Al3Ti. All TEM results are in accordance with the XRD patterns and the EBSD results, which provides strong support to the analysis of the heat treatment and mechanical properties.P Wang would like to thank Dr. X. Zhang, and Dr. L.F. Zhang for the technical assistance and fruitful discussions concerning TEM investigations. Moreover, valuable technical support for EBSD measurements by Dr. Y. Qi, Dr. M.H. Li and Dr. X.H. Gao is gratefully acknowledged. The authors also wish to acknowledge the assistance on HRTEM observations received from the Electron Microscope Center of Shenzhen University. This work was supported by the National Natural Science Foundation of China (NSFC, No. 52105385, and 52005340), the Guangdong Basic and Applied Basic Research Foundation (2020A1515110869 and 2022A1515010781) and Shenzhen international cooperation research (Grant No. GJHZ20190822095418365). I. Okulov acknowledges the financial support provided by the German Science Foundation under the Leibniz Program (Grant MA 3333/13-1). J. Eckert wants to thank the Austrian Academy of Sciences for additional support provided through the Innovation Program.
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