Influence Of Low-melting-point Pr-Cu Alloys On Property Of La-Ce-rich Rare Earth Permanent Magnetic Materials

In this paper,the low-melting-point Pr₈₃Cu₁₇alloys was added to the grain boundary of RE-Fe-B permanent magnets with high La-Ce content（La-Ce/TRE=40 wt.%,TRE:total rare earth）were prepared by powder metallurgy process.Different dependences of microstructure and magnetic properties on Pr₈₃Cu₁₇alloys have been studied by X-ray diffraction（XRD）,scanning electron microscope（SEM）and precision measuring devicefor different temperature curves of permanent magnets（BH instrument）.In addition,its corrosion resistance was also discussed.The following are the main conclusions of this paper:（1）When the addition amount of Pr₈₃Cu₁₇alloys from 0 wt.%to 15 wt.%.The coercivity H_cjincrement from 3.871 k Oe to 10.29 k Oe by～166%.When the addition amount of Pr₈₃Cu₁₇is 5 wt.%,RE-Fe-B permanent magnets obtain better comprehensive magnetic properties.SEM results show that clear,continuous and complete network structure of grain boundary phase is formed in RE-Fe-B permanent magnets.The added Pr₈₃Cu₁₇is mainly distributed at grain boundary to improve the wettability,thereby achieving microstructure optimization and improving demagnetization exchange coupling between grains.In addition,it is also found that Pr element diffuses into main phase grains of RE₂Fe₁₄B that it is form core-shell structure,so that the edges of main phase grains are strengthened to achieve the purpose of increase coercivity H_cj.However,when the addition amount of Pr₈₃Cu₁₇was further increase to 10 and 15 wt.%,the volume ratio of grain boundary phase of permanent magnets increased,result in decrease of remanence B_rand maximum magnetic energy product（BH）_max.Additionally,by measure magnetic properties of RE-Fe-B permanent magnets under high temperature conditions,it is found that as the amount of Pr₈₃Cu₁₇added increases,temperature coefficient of remanenceα_Brand temperature coefficient of coercivityβ_Hcjgradually decrease.The thermal stability of RE-Fe-B permanent magnets decreases.（2）The Pr₈₃Cu₁₇alloys different additions RE-Fe-B permanent magnets with high La-Ce content were subjected to corrosion experiments in 120℃,2 atm and 100%RH.By measure magnetic properties of permanent magnets in different time periods corrosion experiments,when the addition amount of Pr₈₃Cu₁₇in RE-Fe-B permanent magnets is5wt.%,the decrease in magnetic properties of permanent magnets with other Pr₈₃Cu₁₇addition amounts(Pr₈₃Cu₁₇:0,10,15 wt.%)is the smallest.And through scanning electron microscope can observe large number of grain boundary phases that permanent magnets is still in the first stage of corrosion.After 96 h of permanent magnets in the corrosion experiment environment,the weight loss of the permanent magnets with P_r83Cu₁₇alloys addition of 5wt.%measured by weight loss method is 0.057 mg/cm²,which is much smaller than other permanent magnets with Pr₈₃Cu₁₇alloys addition.In short,adding an appropriate amount of Pr₈₃Cu₁₇to RE-Fe-B permanent magnets with high La-Ce content is beneficial to improve the corrosion resistance of permanent magnets.RE-Fe-B permanent magnets were subjected to electrochemical corrosion experiments in 3.5%Na Cl solution.With the increase of the amount of Pr₈₃Cu₁₇added in permanent magnets,the corrosion potential becomes smaller and smaller,decreasing by about 60 m V and the corrosion current becomes larger and larger,indicating that the corrosion resistance of the permanent magnets in the 3.5%Na Cl solution gradually decreases.In this paper,on the premise of not adding heavy rare earth elements,5 wt.%Pr₈₃Cu₁₇is added into grain boundary of the RE-Fe-B permanent magnets with high La-Ce content,which is 60%higher than the coercivity H_cjof the permanent magnets without addition and obtain good comprehensive magnetic properties.At the same time,thermal stability and corrosion resistance were also studied.For the preparation of RE-Fe-B permanent magnets with high La-Ce content that it has certain reference value to realize the application of high-abundance magnets.