Structure and magnetic properties of alloys formed by the laser welding of Sm and Co powders on different substrates

摘要

A modern robotic laser complex with neutral gas supply system of argon to protect the powders from oxidation has been used for laser welding of Sm and Co powders on stainless steel and duralumin substrates. X-ray diffraction investigation of crystalline structure showed that oxidation of mainly Sm occurs during laser welding and following cooling at the standard argon flow. The main ferromagnetic phases: Co and Co-Fe alloy on stainless steel substrate (sample No 3) and SmCo₅ on duralumin substrate (sample No 5) were determined by data of magnetic measurements, including temperature magnetization measurements and magneto-optic Kerr microscopy. It was observed that sample No 3 at T = 300 K showed ferromagnetic properties with small coercive force (about 300 Oe) and high saturation magnetization of 44 emu/g. With temperature decreasing its magnetization monotonically increases to 50 emu/g and coercivity increases in three times that determined with ferromagnetic ordering of Co and Co-Fe alloy grains at various temperatures. The sample 5 showed weak ferromagnetic properties (saturation magnetization of ±27.8 emu/g and coercive force of 130-140 Oe) that determines only by SmCo₅ grains inside the welded layer. Small coercive force for SmCo₅ grains correlates with big sizes of its magnetic domains (20-150 μm).