Study On The Mechanism Properties Of (Ce,Nd)-Fe-B And Effect Of Ce On The Microstructure Of Recycled Sintered Nd-Fe-B Magnets

The sintered(Ce,Nd)-Fe-B magnets have been commercial produced and widely used.Substitution of the cheap Ce for Nd decreased the cost of magnets and realized the balance use of rare-earth resource of China.So far,there are few reports on the mechanical properties of sintered(Ce,Nd)-Fe-B magnets,especially high Ce content magnets,which are important for practical application.In addition,the recycling of sintered Nd-Fe-B magnets is also one of the research hotspots.In this paper,the relationship among mechanical properties,fracture mechanism and microstructure of sintered(Ce,Nd)-Fe-B magnets were investigated.Furthermore,the low cost recycled sintered Nd-Fe-B magnets have been fabricated by Ce-rich alloy addition.The main contents are as follows:The influence of Ce content on mechanical properties of the sintered(Ce,Nd)-Fe-B magnets has been studied.Bending strength and toughness of the sintered(Ce,Nd)-Fe-B magnets were enhanced and the maximum value was achieved when Ce substitution is 15 wt.%.Fine homogenous grain and optimized microstructure were obtained in the magnets.When Ce substitution increased above 15 wt.%,both mechanical properties and the magnetic properties decreased.In addition,flocculent oxide presented in the sintered(Ce,Nd)-Fe-B magnets.These flocculent oxides absorb part of the energy and alleviate the stress concentration on the top of crack during the crack propagating,which toughen the magnets.Transgranular fracture occurred in the fracture with the increase of Ce substitution.During the recycling process,partial RE-rich phase will be oxygenized and consumed,and the densification of the recycled magnets was interfered.The addition of Ce-rich alloy promotes the densifying process and improves the microstructure of the recycled sintered magnets.As a result,the recycled magnets yield better magnetic performance than starting magnets.When sintered at 1080 ℃,the recovery of remanence,coercivity and the maximum energy product of recycled magnets with 5 wt.%Ce-rich alloy addition is 98.8%,104.4%and 104.2%,respectively.When excessive Ce-rich alloy added,remanence of the magnets decreased,the rare-earth rich phase aggregated and coarse grain presented in the magnets.