THE EFFECT OF Mo ADDITION ON COERCIVITY OF NdFeB SINTERED MAGNET PREPARED BY BLENDING METHOD
来源期刊：Acta Metallurgica Sinica2005年第4期
论文作者：J.Q.Zhou M.G. Zhang
Key words：Nd-Fe-B magnet; microstructure; coercivity;
Abstract: Alloy modification, accompanying with proper heat treatment, is commonly used to improve the thermal stability of NdFeB magnet. Traditional alloy modification is performed through melting process with alloy elements to form the multi-alloy. In doing so, these alloy elements not only are introduced into the inter-granular boundaries, but partly into the main phase, thus decreasing to some extent the magnetism of the main phase. In this paper, the blending method is used to prepare the Nd22Fe71B/Mo sintered magnet, and its magnetic properties and microstructures are investigated. The results show that by adding 1.5% (mass fraction) Mo, the intrinsic coercivity Hc of the magnet reaches the maximum value of 1719.36KA/m, while continually increasing the amount of Mo has a less effect on iHc Microstructures analysis indicates that Mo-free Nd-Fe-B magnet has not uniform grains in size, while that with Mo element has uniform grains in size and smooth grain boundaries. Experiments show that after the NdFeB magnet is sintered at 1273K and annealed at 873K, the added Mo element could prevent the equilibrium transformation between the main phase and Nd-rich phase, thus resulting in the precipitation of fine second main phase (Nd2Fe14-xMoxB) from the main phase boundaries, preventing the nucleation and expansion of anti-magnetic domain, and enhancing the coercivity.
J.Q.Zhou1，M.G. Zhang1
(1.Department of Materials Engineering, Taiyuan University of Science and Technology,Taiyuan 030024, China)
Abstract:Alloy modification, accompanying with proper heat treatment, is commonly used to improve the thermal stability of NdFeB magnet. Traditional alloy modification is performed through melting process with alloy elements to form the multi-alloy. In doing so, these alloy elements not only are introduced into the inter-granular boundaries, but partly into the main phase, thus decreasing to some extent the magnetism of the main phase. In this paper, the blending method is used to prepare the Nd22Fe71B/Mo sintered magnet, and its magnetic properties and microstructures are investigated. The results show that by adding 1.5% (mass fraction) Mo, the intrinsic coercivity Hc of the magnet reaches the maximum value of 1719.36KA/m, while continually increasing the amount of Mo has a less effect on iHc Microstructures analysis indicates that Mo-free Nd-Fe-B magnet has not uniform grains in size, while that with Mo element has uniform grains in size and smooth grain boundaries. Experiments show that after the NdFeB magnet is sintered at 1273K and annealed at 873K, the added Mo element could prevent the equilibrium transformation between the main phase and Nd-rich phase, thus resulting in the precipitation of fine second main phase (Nd2Fe14-xMoxB) from the main phase boundaries, preventing the nucleation and expansion of anti-magnetic domain, and enhancing the coercivity.
Key words:Nd-Fe-B magnet; microstructure; coercivity;
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