Grain refinement and coercivity enhancement of sintered Nd–Fe–B alloys by doping eutectic alloy (Nd_0.75Pr_0.25)₇₀Cu_30.

ABSTRACT

A significant enhancement in the coercivity and grain refinement was revealed for the spark plasma sintered NdFeB magnets by doping eutectic alloy (Nd_0.75Pr_0.25)₇₀Cu₃₀ powders. The commercially available NdFeB powders were mixed with (Nd_0.75Pr_0.25)₇₀Cu₃₀ powders (0, 2 and 5 wt.%) and then consolidated by spark plasma sintering at 700°C under 50 MPa. Microstructure analysis shows that the addition of (Nd_0.75Pr_0.25)₇₀Cu₃₀ alloy reduces the formation of coarse grain zone and decreases the average Nd₂Fe₁₄B grain size by intergranular phase modification. The RE-rich phase containing Nd, Pr at the Nd₂Fe₁₄B grain boundary caused the magnetic isolation effect. Hence, the coercivity increased from 18.3 kOe for un-doped NdFeB to 20.3 and 21.6 kOe with doping content of 2 and 5 wt.%, respectively. This study provides an economic way to fabricate sintered NdFeB magnets with enhanced coercivity and homogeneous nanostructure.

KEYWORDS:

• NdFeB magnets
• eutectic alloy
• spark plasma sintering
• grain refinement
• coercivity

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Korea Institute for Advancement of Technology [grant number P0018009] and this work also was supported by the Industrial Strategic Technology Development Program, 20000970, “Development of environmentally friendly pyrometallurgy process for high-purity HREE and materialization” funded By the Ministry of Trade, Industry & Energy (MOTIE, Korea).