# US 2018/0322990 A1 · Rapid consolidation method for preparing bulk metastable iron-rich materials > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0322990 A1 - Document ID: US20180322990A1 - Status: Published application - Kind: A1 - Application number: 16/039,455 - Filed: 2018-07-19 - Published: 2018-11-08 - Earliest claimed: 2015-08-25 - Assignees: GM Global Technology Operations LLC - Applicants: GM Global Technology Operations LLC - Inventors: Chen Zhou; Frederick E. Pinkerton - Web page: https://patentgrep.com/patent/US20180322990A1 ## CPC - H01F 1/0593: {of tetragonal ThMn12-structure} - B22F 3/105: by using electric current {other than for infrared radiant energy}, laser radiation or plasma (B22F3/11 takes precedence){; by ultrasonic bonding (B22F3/115 takes precedence)} - C22C 38/001: {containing N} - C22C 38/005: {containing rare earths, i.e. Sc, Y, Lanthanides} - C22C 38/12: containing tungsten, tantalum, molybdenum, vanadium, or niobium - H01F 1/0557: {sintered} - B22F 1/052: characterised by a mixture of particles of different sizes or by the particle size distribution - B22F 2999/00: Aspects linked to processes or compositions used in powder metallurgy - H01F 41/0266: {Moulding; Pressing (H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11)} - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES - B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER - C22C: ALLOYS (treatment of alloys C21D, C22F) ## Abstract Interstitially modified compounds of rare earth element-containing, iron-rich compounds may be synthesized with a ThMn12 tetragonal crystal structure such that the compounds have useful permanent magnet properties. It is difficult to consolidate particles of the compounds into a bulk shape without altering the composition and magnetic properties of the metastable material. A combination of thermal analysis and crystal structure analysis of each compound may be used to establish heating and consolidation parameters for sintering of the particles into useful magnet shapes. ## Claims ### Claim 1 A method of forming a bulk magnet shape by consolidation of particles having permanent magnet properties, the method comprising: providing particles of a compound expressed by the formula (Ce1−xRx)1+wFe12−yMy, in which compound the value of x is in the range [0, 1], R is an element selected from the group consisting of La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y; w is in the range [−0.1, 0.3], the element M is one or more of Mo, Ti, V, Cr, B, Al, Si, P, S, Sc, Co, Ni, Zn, Ga, Ge, Zr, Nb, Hf, Ta, and W, and the value of y is in the range [1, 4], the particles of the compound having a tetragonal crystal structure, corresponding to the ThMn12 tetragonal crystal structure, and permanent magnet properties; determining a heating temperature, heating period, and compaction pressure at which a volume of the particles of the compound may be consolidated under pressure into a bulk magnet shape, having a density no less than 90% of the density of the original particles, without decomposition of the compound or loss of its tetragonal crystal structure or permanent magnet properties, the determination of the heating temperature, heating period, and compaction pressure for the heating and compaction of the particles of a specific compound into a bulk magnetic shape comprising both thermogravimetric analysis and differential scanning calorimetry analysis of the particles and analysis of the crystal structure of the particles processed by the thermogravimetric and differential scanning calorimetry analyses; and confining a volume of the particles in a die for forming the bulk magnet shape and applying the predetermined compaction pressure for consolidation of the particles while passing a pulsing direct current through the confined volume of particles to heat the particles to the predetermined heating temperature and for the predetermined heating time to produce the consolidated bulk magnet shape while retaining the permanent magnet properties of the original particles of the compound. ### Claim 2 (depends on 1) The method of claim 1 wherein the value of x of the (Ce1−xRx)1+wFe12−yMy compound is in the range [0.6, 1], the value of w is in the range [0.05, 0.15], and the value of y is in the range of [1, 2]. ### Claim 3 (depends on 1) The method of claim 1 wherein the particles of the (Ce1−xRx)1+wFe12−yMy compound have maximum dimensions no greater than forty-five micrometers. ### Claim 4 (depends on 1) The method of claim 1 wherein R is Nd and M is molybdenum in the particles of the (Ce1−xRx)1+wFe12−yMy compound. ### Claim 5 (depends on 4) The method of claim 4 wherein the value of x of the (Ce1−xNdx)1+wFe12−yMoy compound is in the range [0.6, 1], the value of w is in the range [0.05, 0.15], and the value of y is in the range of [1, 2]. ### Claim 6 (depends on 1) The method of claim 1 in which the heating period at the selected heating temperature is no more than ten minutes. ### Claim 7 (depends on 1) The method of claim 1 in which the particles of the (Ce1−xRx)1+wFe12−yMy compound are provided by preparing a molten stoichiometric mixture of the selected proportions of the selected Ce, R, Fe, and M elements of the compound, solidifying the mixture to an ingot, and comminuting the ingot to form particles having maximum dimensions no greater than about forty-five micrometers. ### Claim 8 (depends on 1) The method of claim 1 in which the particles of the (Ce1−xRx)1+wFe12−yMy compound are provided by preparing a molten stoichiometric mixture of the selected proportions of the selected Ce, R, Fe, and M elements of the compound, solidifying the mixture by melt spinning of the molten mixture to form ribbons or particles of the compound, and comminuting the ribbons or particles to smaller particles having maximum dimensions no greater than about forty-five micrometers. ### Claim 9 A method of forming a bulk magnet shape by consolidation of particles having permanent magnet properties, the method comprising: providing particles of a compound expressed by the formula (Ce1−xNdx)1+wFe12−yMoy, in which compound the value of x is in the range [0, 1], w is in the range [−0.1, 0.3], and the value of y is in the range [1, 4], the particles of the compound having a tetragonal crystal structure, corresponding to the ThMn12 tetragonal crystal structure, and permanent magnet properties; determining a heating temperature, heating period, and compaction pressure at which a volume of the particles of the compound may be consolidated under pressure into a bulk magnet shape, having a density no less than 90% of the density of the original particles, without decomposition of the compound or loss of its tetragonal crystal structure or permanent magnet properties, the determination of the heating temperature, heating period, and compaction pressure for the heating and compaction of the particles of a specific compound into a bulk magnetic shape comprising both thermogravimetric analysis and differential scanning calorimetry analysis of the particles and analysis of the crystal structure of the particles processed by the thermogravimetric and differential scanning calorimetry analyses; and confining a volume of the particles in a die for forming the bulk magnet shape and applying the predetermined compaction pressure for consolidation of the particles while passing a pulsing direct current through the confined volume of particles to heat the particles to the predetermined heating temperature and for the predetermined heating time to produce the consolidated bulk magnet shape while retaining the permanent magnet properties of the original particles of the compound. ### Claim 10 (depends on 9) The method of claim 9 wherein the value of x of the (Ce1−xNdx)1+wFe12−yMoy compound is in the range [0.6, 1], the value of w is in the range [0.05, 0.15], and the value of y is in the range of [1, 2]. ### Claim 11 (depends on 9) The method of claim 9 wherein the particles of the (Ce1−xNdx)1+wFe12−yMoy compound have maximum dimensions no greater than forty-five micrometers. ### Claim 12 (depends on 9) The method of claim 9 in which the heating period at the selected heating temperature is no more than ten minutes. ### Claim 13 (depends on 9) The method of claim 9 in which an electron microscopy characterization is used in the crystal structure analysis of particles of a specific compound which were subjected to thermal analysis. ### Claim 14 (depends on 9) The method of claim 9 in which the particles of the (Ce1−xNdx)1+wFe12−yMoy compound are provided by preparing a molten stoichiometric mixture of the selected proportions of the Ce, Nd, Fe, and Mo elements of the compound, solidifying the mixture to an ingot, and comminuting the ingot to form particles of the compound having maximum dimensions no greater than about forty-five micrometers. ### Claim 15 (depends on 9) The method of claim 9 in which the particles of the (Ce1−xNdx)1+wFe12−yMoy compound are provided by preparing a molten stoichiometric mixture of the selected proportions of the Ce, R, Fe, and M elements of the compound, solidifying the mixture by melt spinning of the molten mixture to form ribbons or particles of the compound, and comminuting the ribbons or particles to smaller particles of the compound having maximum dimensions no greater than about forty-five micrometers. ### Claim 16 (depends on 1) A bulk permanent magnet shape consisting of consolidated particles of the compound, (Ce1−xRx)1+wFe12−yMy, as defined in claim 1, when formed in accordance with the process specified in claim 1. ### Claim 17 (depends on 9) A bulk permanent magnet shape consisting of consolidated particles of the compound, (Ce1−xNdx)1+wFe12−yMoy, as defined in claim 9, when formed in accordance with the process specified in claim 9.