Gradient soft magnetic materials produced by additive manufacturing from non-magnetic powders

https://doi.org/10.1016/j.jmatprotec.2021.117393Get rights and content

Highlights

  • Additive manufacturing of gradient soft-magnets.

  • In-situ melting during the direct energy deposition.

  • 3D printing of magnetic materials from paramagnetic powders.

  • The saturated magnetization value of alloys is 49 emu g−1.

Abstract

Additive manufacturing (AM) allows printing parts of complex geometries that cannot be produced by standard technologies. Besides, AM provides the possibility to create gradient materials with different structural and physical properties. We, for the first time, printed gradient soft magnetic materials from paramagnetic powders (316L steel and Cu-12Al-2Fe (in wt.%) aluminium bronze)). The magnetic properties can be adjusted during the in-situ printing process. The saturated magnetization value of alloys reaches 49 emu g−1. The changes in the magnetic properties have been attributed to the formation of the BCC phase after mixing two FCC-dominated powders. Moreover, the phase composition of the obtained gradient materials can be predicted with reasonable accuracy by the CALPHAD approach, thus providing efficient optimization of the performance. The obtained results provide new prospects for printing gradient magnetic alloys.

Introduction

Additive manufacturing (AM) comes into play when conventional methods such as casting, rolling, and stamping fail to create parts of sophisticated geometry. Diegel et al. (2019) summarized a wide range of AM applications from producing a trivial guitar stand to a complex metal hydraulic manifold. However, despite the great potential of the AM current state, the printing of multicomponent alloys with gradient properties is not well studied and requires additional research and development. One of the approaches to perform gradient materials printing is the premixing blend of the original materials. Shen et al. (2021) demonstrated the possibility of using innovative combined cable wire arc 3D printing technology to produce parts from multiple filaments composed of 5 elements high-entropy alloy (Al-Co-Cr-Fe-Ni) and the possibility of changing mechanical properties of a printed model by varying printing speed. Dobbelstein et al. (2019) used multiple compositions of preblended TiZrNbTa powders to produce graded high entropy samples and to find a composition with better printability for laser material deposition process and better mechanical properties. Chen et al. (2020) used a mixture of high entropy CoCrFeNi pre-alloyed powder with Mn powder for selective laser melting process with varying build parameters and achieved good printability and successful in-situ alloying.

However, this approach does not allow controlling chemical composition during the printing process, while in-situ mixing of the materials during printing allows obtaining gradient materials and creating new alloys. Recently, Melia et al. (2020) presented the homogeneous MoNbTaW alloy produced by AM technique using four powders of pure metals as a feedstock. Moorehead et al. (2020) also demonstrated the possibility to obtain the single solid solution for the MoNbTaW system using Direct Energy Deposition (DED) technique. Their results have a good agreement with a CALPHAD calculation. DED is one of the AM techniques that can produce such graded materials, which allows to evade the use of complex casting technologies or spark plasma sintering. Mixing materials during the printing process is very promising for the manufacturing of magnetic alloys.

Another perspective AM technology for the production of magnetic materials is Laser-Powder Bed Fusion (LPBF). Volegov et al. (2020) demonstrated the possibility to use LPBF to print hard magnets with high coercivity from NdFeB-based magnetic powder. Schönrath et al. (2019) studied the effects of selective laser melting parameters on magnetic properties of premixed Fe and Ni powders. Quite high saturated magnetization values were achieved due to the fact that he used two ferromagnetic powders. Garibaldi et al. (2018) demonstrated the ability to change magnetic properties of 3D printed FeSi samples by heat treatment. Kang et al. (2018) demonstrated the difference in magnetic properties of Fe-Ni-Si samples produced by selective laser melting with different build parameters. The variation of printing conditions in LPBF changes the nitrogen content in high-nitrogen steel and, as a result, leads to the formation of para- or ferromagnetic properties. Arabi-Hashemi et al. (2020) introduced in-situ alloying by precisely controlled selective laser melting parameters to modify magnetic properties inside a single 3D printed part.

DED technology is able to print gradient materials AlxCuCrFeNi2, FexCo100-x, FexNi100-x, Fe–Si–B–Nb–Cu. Borkar et al. (2017, 2016) successfully built functionally graded soft-magnets with Fe–Si–B–Cu–Nb and Al-Cr-Cu-Fe-Ni alloys by varying supply rate of elemental powders during the direct energy deposition process. Toman et al. (2018) performed DED printing of magnetic shape memory Ni-Mn-Ga alloy. Magnetic analysis of this alloy showed that heat treatment increases saturated magnetization. Kustas et al. (2019) showed effects of 3D printing parameters on microstructure of soft ferromagnetic FeCo alloy. Mikler et al. (2017) demonstrated effects of laser speed and laser power on magnetic properties of DED ferromagnetic alloy Fe-30at%Ni.

All discussed ways to produce magnetic samples are using ferromagnetic consumable materials. However, utilization of ferromagnetic metal powders in DED technology may lead to clogging of the powder feeding system on some machines due to magnetization of the feeding system and/or metal parts magnetization by the powder. LPBF technology requires demagnetization of build substrate and metal parts inside a build chamber to avoid uneven ferromagnetic powder layering. In-situ production of ferromagnetic parts from paramagnetic powders is the potential way to address these issues.

In this paper, for the first time, we demonstrate that the use of in-situ melting in the printing process allows the printing of soft magnets from non-magnetic powders. Two paramagnetic metal powders Aluminum-Bronze and SS 316L were used during this process with variable feed rates to achieve different printing material compositions and different magnetic properties. The results of this work refer to gradient materials as a potential input for the fabrication of parts with magnetization varying from 0 to 49 emu g−1 and quite low coercivity varying from 43 to 81 G.

Section snippets

Experimental section

The samples were created on the Insstek MX-1000 printer based on direct energy deposition technology. Three feeders with different powder compositions allow printing gradient structures with various concentrations of elements. Aluminum bronze (Cu-12Al-2Fe (in wt.%), denoted as Al-Bronze hereinafter) and 316L stainless steel (SS) powders produced by Praxair and Höganäs were used. The powder size distribution varies in the range of 45−145 μm. The printing regime is as follows: laser power of 420

Results and discussion

Fig. 1 demonstrates the SEM images of the powder and particle size distribution (PSD). The average size of 316L is ∼ 83 μm (Fig. 1a), while the average size of the Al-Bronze powder is 95 μm (Fig. 1c). PSD has a different distribution that is demonstrated in Fig. 1b), d). The scheme of the experiment is presented in Fig. 2a. The Insstek MX 1000 has 3 feeders for producing the trinary alloys from the initial powders. In our experiments, we used two feeders filled with 316L and aluminium bronze

Conclusions

To sum up, for the first time, we have demonstrated the possibility of printing gradient soft magnetic materials using in-situ melting during direct energy deposition. The paramagnetic powders have been used for the production of soft magnetic materials. The addition of Al-bronze to 316L transforms the single FCC phase structure to the mixture of the FCC and BCC phases. The achieved maximum fraction of the BCC phase was 59 % in the perpendicular build direction of the (Al-bronze)50(316L)50

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

CRediT authorship contribution statement

O.N. Dubinin: Methodology, Investigation, Writing – original draft. D.A. Chernodubov: Data curation, Investigation. Y.O. Kuzminova: Data curation, Investigation. D.G. Shaysultanov: Data curation, Investigation. I.S. Akhatov: Supervision. N.D. Stepanov: Data curation, Writing – original draft. S.A. Evlashin: Conceptualization, Writing – original draft.

Declaration of Competing Interest

The authors declare no known financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The research is funded by the Ministry of Science and Higher Education of the Russian Federation as part of World-class Research Center program: Advanced Digital Technologies (contract No. 075-15-2020-903 dated 16.11.2020)

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