The effect of CuAl addition on the magnetic property, thermal stability and corrosion resistance of the sintered NdFeB magnets.

To improve the coercivity of the Nd-Fe-B sintered magnets, the Cu_29.8Al_70.2 (at.%) powders with low melting point were introduced into the Nd-Fe-B magnets. The magnetic properties, microstructure, thermal stability and corrosion behavior of the sintered magnets with different amount of Cu_29.8Al_70.2 (0,0.25,0.50,0.75,1.0 wt.%) were investigated. When the amount of doped Cu_29.8Al_70.2 was less than 0.75 wt.%, the coercivity was improved, especially that of the magnets with 0.25 wt.% Cu_29.8Al_70.2, markedly increased to 13.97 kOe from 12.67 kOe (without CuAl). The improvement of magnetic properties could be attributed to enhanced wettability between Nd₂Fe₁₄B phase and Nd-rich phase and decreased exchange coupling between grains, which depended on the optimization of grain boundary microstructure and their distribution by codoping Cu and Al. With the addition of 0-1.0 wt.% Cu_29.8Al_70.2 powders, the reversible temperature coefficients of remanence and coercivity of the magnets could be also improved. The corrosion resistances was also found to be improved through small addition of Cu_29.8Al_70.2 powder in 3.5 wt.% NaCl solution by electrochemical and immersion tests, which could be due to the enhancement of the Nd-rich intergranular phase by addition Cu_29.8Al_70.2. [ABSTRACT FROM AUTHOR]