Comparative study of laser powder fusing of Sm-Co and Sm-Fe systems on the duralumin substrate: microstructure and magnetic properties

A robotic laser technological complex has been used for the laser powder fusing (LPF) of samarium (Sm) and iron (Fe) or Sm and cobalt (Co) powders on duralumin (AMG-3) substrates in argon flow conditions for the creation of thick (0.3–0.5 mm) ferromagnetic coatings. For the Sm-Fe system in the first step of Sm powder laser fusing the chemical interaction between Sm powder and Al atoms from the melted AMG-3 substrate resulted in the formation of Al2Sm in both cases: with and without perpendicular magnetic field (samples Nos. 6 and 4). The perpendicular magnetic field during LPF on the AMG-3 substrate resulted in the formation of the additional compound Fe5Al8 for sample No. 6. The formation of SmxFe alloy in the second step of Fe LPF was blocked due to the lower chemical activity of Fe atoms compared to Sm, and the high resistance of Al2Sm. But for Sm-Co system the interaction between Sm and Co atoms was not blocked and SmCo5 as a majority crystalline phase was formed. Samples Nos. 4 and 6 based on the Al2Sm and Fe5Al8 compounds were very weak ferromagnetic phases at 300 K with low coercivity, but a strong ferromagnetic ordering with Curie temperature of 70 K was observed at lower temperatures. This ordering increased by 100 times the saturation magnetisation, residual magnetisation and coercivity at 4K. The mechanism of such type of magnetic ordering is not clear at present. The two chopped pieces of the sample No. 5 showed ferromagnetic properties (saturation magnetization of (±27,8 emu/g and ±20.5 emu/g) and coercivities of 130-140 Oe and 300-320 Oe ) that determines only by SmCo5 grains inside the fused layer. The increase of coercivity for SmCo5 grains correlates with increase of area of grain boundaries inside the fused layer.

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