Laser Additive Manufacturing of Fe-Based Magnetic Amorphous Alloys

Abstract

Fe-based amorphous materials offer new opportunities for magnetic sensors, actuators, and magnetostrictive transducers due to their high saturation magnetostriction (λs = 20–40 ppm) and low coercive field compared with polycrystalline Fe-based alloys, which have high magnetostriction but large coercive fields and Co-based amorphous alloys with small magnetostriction (λs = −3 to −5 ppm). Additive layer manufacturing (ALM) offers a new fabrication technique for more complex net-shaping designs. This paper reviews the two different ALM techniques that have been used to fabricate Fe-based amorphous magnetic materials, including the structural and magnetic properties. Selective laser melting (SLM)—a powder-bed fusion technique—and laser-engineered net shaping (LENS)—a directed energy deposition method—have both been utilised to fabricate amorphous alloys, owing to their high availability and low cost within the literature. Two different scanning strategies have been introduced by using the SLM technique. The first strategy is a double-scanning strategy, which gives rise to maximum relative density of 96% and corresponding magnetic saturation of 1.22 T. It also improved the glassy phase content by an order of magnitude of 47%, as well as improving magnetic properties (decreasing coercivity to 1591.5 A/m and increasing magnetic permeability to around 100 at 100 Hz). The second is a novel scanning strategy, which involves two-step melting: preliminary laser melting and short pulse amorphisation. This increased the amorphous phase fraction to a value of up to 89.6%, and relative density up to 94.1%, and lowered coercivity to 238 A/m. On the other hand, the LENS technique has not been utilised as much as SLM in the production of amorphous alloys owing to its lower geometric accuracy (0.25 mm) and lower surface quality, despite its benefits such as providing superior mechanical properties, controlled composition and microstructure. As a result, it has been commonly used for large parts with low complexity and for repairing them, limiting the production of amorphous alloys because of the size limitation. This paper provides a comprehensive review of these techniques for Fe-based amorphous magnetic materials.

Additive Manufacturing of Bulk Metallic Glasses—Process, Challenges and Properties: A Review

“…Fe-based MGs have excellent magnetic properties such as low coercivity, high magnetostriction, and magnetic permeability. These properties are attributed to the lack of crystal-related defects, such as dislocations and grain boundaries [25]. Due to the above-mentioned properties, Fe-based MGs are used in sensors, actuators, transformers, and communication equipment [122].…”

“…In the past decade, several reviews have been published on AM of BMGs [18,19,[24][25][26][27]. Lavery and Williams [19] and Li [24] reported short sections on the topic in 2017, when limited research had been undertaken.…”

“…Liu et al [18] focused mainly on the crystallization of BMGs fabricated via laser powder-bed fusion (LPBF). Ozden and Morley [25] restricted their review to AM of Fe-based magnetic BMGs. Zhang et al [27] investigated different techniques used for AM of BMGs mentioned some of the challenges, and focused mainly on the mechanical properties of BMGs and BMG composites.…”

Structure, Mechanical and Magnetic Properties of Selective Laser Melted Fe-Si-B Alloy

“…High magnetic properties are achieved with amorphous phases, and materials consisting of nanocrystalline inclusions evenly distributed in the amorphous matrix are also known. Currently, amorphous and nanocrystalline materials produced by additive manufacturing techniques are being investigated by many research groups worldwide [1,[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. The problem of obtaining samples with amorphous phase from iron-based soft-magnetic alloys using SLM has been solved with varying degrees of success by selecting process parameters [1,4,11,14,18,19] and by developing and applying specially designed materials and laser beam scanning strategies [4,10,11,19].…”

Special Issue: Materials, Design and Process Development for Additive Manufacturing

“…This type of material has a significantly higher level of soft-magnetic properties compared to crystalline analogues. High cooling rates are typical for the selective laser melting process, but to reduce crystallinity and increase magnetic properties sometimes it is necessary to use nonstandard build strategies of laser scanning [ 17 ]. The first strategy was double scanning of each layer, the use of which enabled the researchers to achieve a maximum relative density of 96% and saturation magnetization of 1.22 T. The usage of this scanning strategy also increased the amorphous phase content of samples to 47% and reduced coercivity.…”