Borukh I. Influence of hydrogen treatment on structure and magnetic properties of materials based on Nd2Fe14B and SmCo5 intermetallics

The thesis for a degree of Candidate of Sciences (Engineering) is devoted to the development of the method of obtaining sintered nanostructured magnets from rare earth – transition metal alloys using hydrogen – initiated phase transformations – the HDDR method. The conditions of processing the Nd11,7Fe82,3B6, Nd16Fe76B8; Nd11,7Fe81,1Zr1,2B6, Nd16Fe73,9Zr2,1B8 and Sm(Co,T)5, T=Zr, V, Ti ferromagnetic materials at separate stages of production of sintered magnets: grinding, pressing and sintering, are investigated. The relationship between the parameters of grinding alloys and the parameters of hydrogen treatment to obtain magnetically anisotropic materials with crushed to the nanolevel microstructure is studied. A method for sintering the studied ferromagnetic alloys at low temperatures in hydrogen to obtain nanostructured materials with low porosity is developed. It is found that to obtain sintered nanostructured magnets, materials based on Nd2Fe14B must be treated in hydrogen under pressure up to 0.05 MPa at a temperature of 700°C, in vacuum- at a temperature of 850°C. Materials based on SmCo5 must be treated in hydrogen under a pressure of 0.1-0.5 MPa at a temperature of 650°C, in vacuum – at a temperature of 950°C. The prospects of heat treatment of sintered magnets in hydrogen to increase their magnetic properties with the achievement of the coercive force of SmCo5 magnets of about 50 kE are shown. For the first time, a high coercivity of 49.7 kOe is obtained in the HDDR treatment of SmCo5 and for the first time the sintering temperature is reduced to 950°C during sintering of pressed elements from powders of SmCo5, Sm(Co,Zr)5, Nd11,7Fe81,1Zr1,2B6, Nd16Fe73,9Zr2,1B8 alloys. The conditions for processing the Nd-Fe-B-Zr alloys in hydrogen under which there are the remains of the Nd2Fe14B ferromagnetic phase and after which, due to processing by HDDR, the Nd-Fe-B-Zr alloys are nanostructured and magnetically anisotropic, are established. The grinding conditions of Sm-Co-Zr alloys after which the grinded powders are magnetically anisotropic are studied. Practical recommendations proposed in the research are protected by two patents of Ukraine.