A. E. Ray

The development of high energy product permanent magnets from 2:17 RE-TM alloys

The remanence, B r , of sintered 2:17 RE-TM permanent magnets depends on saturation magnetization, M s , particle alignment, and packing density. Methods to estimate upper bounds for M s and energy product, (BH) max , as a function of composition are presented. As B r is limited by processing variables, (BH) max is limited by intrinsic coercivity, M H c , and loop squareness. The coercivities of the 2:17 RE-TM permanent magnets are controlled by the alloy microstructures and the compositions of the phases comprising these microstructures. Some aspects of the response of these alloy systems to compositional and heat treating variables are discussed in light of a model proposed for their metallurgical behavior.

A revised model for the metallurgical behavior of 2 : 17-type permanent magnet alloys

The 2:17 magnet alloys form a complex metallurgical system with a large number of interactive compositional and heat‐treating variables. A model for the metallurgical behavior of these alloys was proposed by the author in 1983. Subsequent experiments designed to test that model have verified some aspects, significantly modified others, and added much detail. The current version of the model is reported.

Magnetic properties of rare earth-cobalt phases R 5 Co 19

Phases with the stoichiometry R 5 Co 19 have been observed in the rare earth-cobalt systems with R = La, Ce, Pr, and Nd. These phases may play a significant role in the development of coercive force in RCo 5 -based permanent magnets containing the light rare earths, particularly mischmetal. The present paper reports Curie temperatures, saturation magnetizations, and the results of anisotropy field measurements made on alloy powders of these phases.

Characterisation of rare earth-transition metal alloys with resistivity measurements

Precipitation hardening in Sm/sub 2/(Co,Fe,Cu,Zr)/sub 17/-type alloys and commercial magnets and magnetic and phase transitions and hydrogen absorption and desorption of Nd-Fe-B-type alloys are investigated by electrical resistivity measurements. Changes in the resistivity of a Sm(Co/sub .63/Fe/sub .27/Cu/sub .08/Zr/sub .02/)/sub 8.35/ alloy after solid solution treatment of 1155 degrees C and during isothermal aging at 800 degrees C can be attributed to the precipitation of the platelet and the grain boundary phase. In commercial sintered magnets, an anisotropy in the electrical resistivity is found for the fully heat treated condition when measuring parallel to either the basal plane or the c-axis. A Nd/sub 14.68/Dy/sub 0.94/Al/sub 0.62/-Nb/sub 0.5/B/sub 6.79/ alloy is studied employing in-situ measurements of the electrical resistivity and the Curie-point. The formation of the liquid grain boundary phase and the HDDR (hydrogenation, disproportionation, desorption, recombination)-process are observed. >

The effects of various alloying elements on modifying the elevated temperature magnetic properties of sintered Nd‐Fe‐B magnets

The effects of the alloying elements Co, Dy, Er, Al, and Nb on modifying the elevated temperature properties of sintered Nd‐Fe‐B–based permanent magnets have been studied in our laboratory. The results are summarized and analyzed. Small Nb additions increase coercivity and improve elevated temperature properties. Higher Nb additions lead to decomposition of the 2:14:1 phase into a 2:17 phase and a new magnetic phase with a Curie point around 350 °C. The effectiveness of Nb additions appears to be associated with the rare‐earth content of the magnets.

Elevated temperature study of Nd‐Fe‐B–based magnets with cobalt and dysprosium additions

This paper discusses the elevated temperature performance of Nd‐Fe‐B magnets containing 0–15 wt. % cobalt substitutions for iron and 0–10 wt. % dysprosium substitutions for neodymium. Test samples were prepared using conventional powder metallurgy techniques. Elevated temperature hysteresis loop and open‐circuit measurements were performed on the samples to investigate irreversible losses and long term aging losses at 150 °C. Magnets with high amounts of both cobalt and dysprosium exhibited lower losses of coercivity and magnetization. Dysprosium had more influence on the elevated temperature performance of the material than did cobalt.

Magnetic and metallurgical properties of Sm(Co,Fe,Cu,Zr) z alloys near z = 8.5

Very large intrinsic coercivities, ranging from 28-32kOe, combined with saturation inductions ranging from 11.6- 12.1kG have been obtained in bulk alloys corresponding to the compositions Sm(Co .90-v Fe v Cu .08 Zr .02 ) 8.35 with v=0.23- 0.30. We do not observe a drop in 4πM s as M H c reaches high levels nor a significant drop in M H c at high Fe contents.

Temperature‐compensated 2:17‐type permanent magnets with improved magnetic properties

Computer programs have been developed to predict temperature coefficients of saturation magnetization for (Sm1−xGdx)2Tm17 magnets with higher Fe content from temperature‐dependent magnetic properties of single rare‐earth compositions. Very good agreement was obtained between the calculated and measured data. The composition Sm0.54Gd0.46 (Co0.63Fe0.29Cu0.06Zr0.02)7.69 exhibits a nearly zero temperature coefficient of magnetization from −60 to 150 °C. Its maximum energy product remains 16–17 MGOe in the temperature range of 20–200 °C. A room‐temperature energy product of 19 MGOe was attained for the composition Sm0.55Gd0.45(Co0.608Fe0.316Zr0.02)7.72.

Fe site populations in Sm2(Co, Fe)17 and Sm(Co, Fe, Cu, Zr)8.35 alloys

Abstract We have investigated the crystallographic site distribution of Fe atoms in Sm 2 (Co 1−x Fe x ) 17 and Sm(Co 0.90−v Fe v Cu 0.08 Zr 0.02 ) 8.35 alloys by means of Mossbauer spectroscopy. Fe shows a strong preference for 2c (dumbbell) sites in the former system, but in the multicomponent alloys such preference is reduced. This result gives support to a model proposed by Ray, according to which Zr-vacancy pairs displace FeFe dumbbell pairs during the solutionizing heat treatment of these permanent-magnet materials.

Magnetic saturation and anisotropy of La 2 Co 7 , Pr 2 Co 7 , and Nd 2 Co 7

Room-temperature lattice parameters, density, saturation magnetization and magneto-crystalline anisotropy data are reported for the intermetallic compounds La 2 Co 7 , Pr 2 Co 7 , and Nd 2 Co 7 . Powder x-ray techniques were used to determine lattice constants and the easy direction of magnetization. Saturation values and anisotropy constants were derived from c-axis and basal-plane moment vs. field measurements on small single-crystal fragments of arc-melted and annealed alloy buttons.