Magnetic properties of Mn-Al alloy after HPT deformation

• Published in: Materials letters 2020-08, Vol.272, p.127864, Article 127864
• Main Authors: Gorshenkov, M.V., Karpenkov, D.Y., Sundeev, R.V., Cheverikin, V.V., Shchetinin, I.V.
• Format: Article
• Language: English
• Subjects: Aluminum base alloys; Coercivity; Crystal defects; Deformation; Diameters; Domain walls; Heat treatment; High-pressure torsion; HPT; Magnetic properties; Magnetism; Manganese; Materials science; MnAl magnet; Permanent magnets; Rare-earth free magnets; Room temperature
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2020.127864

•HPT deformation was employed for production of bulk disk-shaped Mn-Al magnets.•The coercive force Hc = 0.37 T at Ms = 0.49 T was achieved for deformation e = 5.16.•Both twinning and dislocation mobility occurs during HPT.•HPT deformation decrease stability of metastable τ -phase. In this study, we reported on the possibility to produce a bulk permanent magnet based on Mn55Al43C2 alloy by high-pressure torsion (HPT) deformation. The results show that using room temperature HPT deformation it is possible to obtain a small volume disk-shaped magnetic sample of 0.5 mm thickness and 8 mm diameter deformed for 1, 3 and 5 turns. The maximum coercive force of Hc = 0.37 T (3.7 kOe) at Ms = 0.49 T (75 emu/g) was obtained for the sample deformed for 5 turns (e = 5.16). The reason for enhance of coercive force is accumulation of crystalline defects acting as pinning centers for domain walls. Subsequent heat-treatment of deformed samples at temperature ranging 500–650 °C reduces the coercive force down to 0.24 T (2.4 kOe) with the simultaneous recovery of saturation Ms almost up to initial value 0.75 T (115 emu/g).