Phase transformation and magnetic properties of rapidly solidified Mn-Al-C alloys modified with Zr

Abstract

Mn 54Àx Al 43 C 3 Zr x (x ¼ 1, 3) alloys were prepared by rapid solidification followed by heat treatment to produce the ferromagnetic s phase. The substitution of Zr for Mn in the structure resulted in an increase of the saturation magnetization (M s ) compared to that of Mn 54 Al 43 C 3 . While the highest M s (128 6 1 emu/g) was obtained in Mn 53 Al 43 C 3 Zr 1 , the coercivity was also improved to 1.62 kOe, compared to 1.25 kOe for Mn 54 Al 43 C 3 . To further improve the coercivity through grain refinement, additional C (1%, 3%, 5%, and 7%) was added to Mn 53 Al 43 C 3 Zr 1 . An increase in the coercivity was observed due to a decrease of grain size and the formation of nonmagnetic phases, which reduced the magnetostatic interactions between the s-phase grains. However, excess C reduced the saturation magnetization due to the formation of the other non-ferromagnetic phases, including e, c 2 , and b phases. V C 2015 AIP Publishing LLC. [http://dx

In situ Observation of Phase Transformation in MnAl(C) Magnetic Materials

“…An M s of ~128 Am 2 /kg was reported in the samples with Zr substitution for Mn and high C content samples with 72 wt. % Mn [ 13 , 25 ]. We also studied the effect of magnetic field during annealing on the phase transformation and found that the magnetic field has little effect on the saturation magnetization of the final product.…”

“…The L1 0 structured τ-phase MnAl, usually prepared by annealing the hexagonal ε-phase MnAl at moderate temperatures, is attracting increasing research interests over decades for its low cost and high performance as promising rare earth free magnets [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. The metastable nature of τ-MnAl usually results in its decomposition during prolonged annealing or high temperature processing [ 3 , 4 , 5 , 6 ].…”

High Coercivity in MnAl Disc Prepared by Severe Plastic Deformation

“…Most of the previous studies on MnAl‐based alloys were focused on achieving a higher fraction of τ ‐phase and thus a higher saturation magnetization ( M s ), understanding the ε → τ phase transformation mechanism, and enhancing the magnetic performance, particularly the coercivity, via various methods . So far high‐purity τ‐phase has been prepared and there is not much space for improving M s . Currently, the ε → τ phase transformation mechanism is also well‐known and the ε → τ process can be controlled by optimized annealing conditions .…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Most of the previous studies on MnAl-based alloys were focused on achieving a higher fraction of τ-phase and thus a higher saturation magnetization (M s ), [3] understanding the ε ! τ phase transformation mechanism, [4,5] and enhancing the magnetic performance, particularly the coercivity, via various methods. [3,[6][7][8] So far high-purity τ-phase has been prepared and there is not much space for improving M s .…”

“…[3,[6][7][8] So far high-purity τ-phase has been prepared and there is not much space for improving M s . [4,5,9] Currently, the ε ! τ phase transformation mechanism is also well-known and the ε !…”