Effect of Fe and Si on properties of squeezed aluminum metal matrix Nd-Fe-B composite magnets

The present work studies the effect of Fe and Si on the microstructure, mechanical and magnetic properties of three aluminium metal matrix Nd-Fe-B composite magnets. The composite magnets are prepared by squeezing three aluminium alloys (pure Al, A356 alloy and A356+0.8%Fe alloy) into preformed Nd-Fe-B magnetic powder. The results indicate that the pure Al based Nd-Fe-B composite magnet has the most active reaction layer. However, the thickness of the reaction layer decreases as the Fe content in the matrix increases. In the composite magnet made of the A356 aluminium alloy matrix, Si elements are concentrated near the interfaces, forming a needle like FeSiAl₅ phase. Increasing the Fe content in aluminium matrix increases the remanence Br of the composite magnets from 0.51 to 0.66 T, and increases the energy product (BH)_max from 36.8 to 63.2 kJ m^-3. The intrinsic coercivity iHc of these composite magnets is nearly the same as the original magnetic powder.