Magnetic Properties and Phase Transformations of Bulk Amorphous Fe-Based Alloys Obtained by Different Techniques

Abstract

Bulk amorphous Fe 65.5 Cr 4 Mo 4 Ga 4 P 12 C 5 B 5.5 rods with diameters of 1.5-3 mm were prepared by copper mold casting. Besides casting, bulk amorphous Fe 77 Al 2.14 Ga 0.86 P 8.4 C 5 B 4 Si 2.6 samples in the shape of discs (diameter of 10 mm and thickness of 3 mm) were prepared from melt-spun ribbons by high-energy ball milling and subsequent compaction of the resulting powders in the supercooled liquid region. The ascast amorphous FeCrMoGaPCB samples exhibit a low coercivity, below 10 A·m −1 . In the case of the FeAlGaPCBSi alloy, the milling-induced stress causes significant differences in coercivity between the ribbons and the powders. The relatively low coercivity of about 5-10 A·m −1 characteristic for the melt-spun ribbons increases after 1 hour of ball milling to a value of about 2200 A·m −1 . Subsequent annealing of the ball-milled powders leads to a decrease of H c by a factor of 10 to about 220-250 A·m −1 . The bulk samples prepared by hot pressing of the crushed ribbons show a coercivity of about 120-140 A·m −1 . For both alloys, thermal stability measurements show a distinct glass transition, followed by a supercooled liquid region of 60 K for Fe 65.5 Cr 4 Mo 4 Ga 4 P 12 C 5 B 5.5 and of 30 K for Fe 77 Al 2.14 Ga 0.86 P 8.4 C 5 B 4 Si 2.6 . For the Fe 65.5 Cr 4 Mo 4 Ga 4 P 12 C 5 B 5.5 alloy, crystallization of the amorphous phase as observed by in-situ X-ray diffraction measurements in transmission configuration occurs via the formation of a metastable intermediate phase. The phases observed in the crystalline state obtained by heating do not correspond to those occurring after slow cooling.

Electrochemical response of Fe65.5Cr4Mo4Ga4P12 C5B5.5 bulk amorphous alloy in different aqueous media

“…Multicomponent iron-based alloy systems have been developed with large glass forming abilities and various alloy systems have been reported that are amorphous in bulk form [1 -3]. The Fe 65.5 Cr 4 Mo 4-Ga 4 P 12 C 5 B 5.5 amorphous alloy chosen for this study exhibits good soft magnetic properties, characterized by a low coercive force and a high permeability [4]. Using the copper mold casting method, such alloys can be cast in the form of bulk specimens directly suitable for use in various devices.…”

“…While the excellent corrosion resistance of amorphous Fe-Cr-P-C alloys was reported [5], such alloys could not be prepared in bulk form due to their low glass-forming ability. The Fe-Cr-Mo-metalloids bulk amorphous system has been examined for its corrosion resistance but in a very limited way [4,9]. The alloys used had very high levels of chromium and molybdenum, which naturally resulted in very good corrosion resistance of such alloys.…”

Soft Magnetic Materials in a Bulk Form Prepared by Powder Compaction

“…Milling techniques offer possibilities for the preparation of alloys (however in powder form), which are impossible to produce by conventional alloying methods. Bulk materials in various shapes can be produced by powder compaction [8]. The aim of our work is to prepare amorphous, nanocrystalline and microcrystalline bulk material by the compaction of a short-time ball milled powder of various chemical compositions and to investigate magnetic properties of such a material.…”

Bulk Glassy Fe–Mo–Ga–P–C–B–Si Alloys with High Glass-Forming Ability and Good Soft Magnetic Properties

“…[3][4][5][6][7][8][9][10] However, it is always a discrepancy for increasing glass-forming ability (GFA) and saturation magnetization (I s ) at the same time, because additions of glassforming elements decrease Fe content, which results in the decrease of I s . Therefore, many Fe-based BGAs with large supercooled liquid region (ÁT x ) before crystallization defined by the difference between glass transition temperature (T g ) and crystallization temperature (T x ), exhibit low I s below 1 T, 3,[6][7][8] that needs to improve more when using as magnetic materials for most of the application fields. With the aim of synthesizing large size Fe-based BGAs with high I s , we developed Fe 65 Co 10 Ga 5 P 12 C 4 B 4 and Fe 77 Ga 3 P 9:5 -C 4 B 4 Si 2:5 BGAs which exhibit the high I s of 1.2 and 1.35 T, as well as large ÁT x of 45 and 50 K, respectively, 11,12) that allowed us to synthesize Fe-based BGAs successfully with diameters up to 20 mm by the consolidation method utilizing significant viscous flowability in the supercooled liquid state.…”